Fix#22724 by adding an Open Resource button
Add a Remove button to each tree item
Remove the old Remove button and its useless code
Adjust columns min width
Remove Resource names and move icons to the left
Add a Resource icon fallback
the tile cursor did not follow the mouse cursor, and the tile grid was displayed wrong,
because the forward_canvas_draw_over_viewport function used the wrong xform and thus its
map_to_world is not the inverse of the mouse interactor world_to_map, making the tiles
draw from 0,0 of the screen instead of 0,0 of the tile map (which is in a different place)
Fixes the following GCC 8 warnings:
```
core/image.cpp:730:44: warning: 'mip1_weight' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/image.cpp:293:20: warning: 'mip2' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/image.cpp:293:20: warning: 'mip1' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/audio_stream_preview.cpp:58:19: warning: 'vmax' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/audio_stream_preview.cpp:85:19: warning: 'vmin' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/editor_themes.cpp:306:53: warning: 'preset_contrast' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/plugins/animation_blend_space_2d_editor.cpp:459:27: warning: 'prev_idx' may be used uninitialized in this function [-Wmaybe-uninitialized]
editor/plugins/animation_blend_space_2d_editor.cpp:443:27: warning: 'prev_idx' may be used uninitialized in this function [-Wmaybe-uninitialized]
main/tests/test_oa_hash_map.cpp:57:29: warning: 'value' may be used uninitialized in this function [-Wmaybe-uninitialized]
modules/csg/csg.cpp:764:40: warning: 'max_angle' may be used uninitialized in this function [-Wmaybe-uninitialized]
modules/csg/csg_shape.cpp:1945:3: warning: 'face_count' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/3d/voxel_light_baker.cpp:1593:8: warning: 'cone_aperture' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/3d/voxel_light_baker.cpp:1592:6: warning: 'cone_dir_count' may be used uninitialized in this function [-Wmaybe-uninitialized]
scene/animation/animation_blend_space_2d.cpp:471:8: warning: 'mind' may be used uninitialized in this function [-Wmaybe-uninitialized]
core/os/memory.cpp:94: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
core/os/memory.cpp:95: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
core/os/memory.cpp:98: warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
```
Disabled signed/unsigned warnings like for GCC/Clang
(warning C4018: '>=': signed/unsigned mismatch).
Fixes the following MSVC 2017 warnings:
```
core\image.cpp(999): warning C4804: '>': unsafe use of type 'bool' in operation
core\io\compression.cpp(178): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
editor\doc\doc_dump.cpp(226): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(289): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(298): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
editor\editor_themes.cpp(379): warning C4805: '==': unsafe mix of type 'int' and type 'bool' in operation
```
Fixes the following Clang 7 warnings:
```
editor/editor_help.h:123:7: warning: 'EditorHelpIndex::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/editor_help.h:95:7: warning: 'EditorHelpSearch::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/editor_help.h:96:7: warning: 'EditorHelpSearch::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/plugins/curve_editor_plugin.h:141:15: warning: 'CurvePreviewGenerator::generate' hides overloaded virtual function [-Woverloaded-virtual]
editor/plugins/script_editor_plugin.h:70:7: warning: 'ScriptEditorQuickOpen::popup' hides overloaded virtual function [-Woverloaded-virtual]
editor/quick_open.h:69:7: warning: 'EditorQuickOpen::popup' hides overloaded virtual function [-Woverloaded-virtual]
main/tests/test_io.cpp:53:15: warning: 'TestIO::TestMainLoop::input_event' hides overloaded virtual function [-Woverloaded-virtual]
servers/audio/effects/audio_effect_record.h:69:15: warning: 'AudioEffectRecordInstance::process_silence' hides overloaded virtual function [-Woverloaded-virtual]
core/os/memory.h:119:2: warning: destructor called on non-final 'ContextGL_X11' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'EditorScriptCodeCompletionCache' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'Engine' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'PhysicalBone::JointData' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'VisualServerScene' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
core/os/memory.h:119:2: warning: destructor called on non-final 'VisualServerViewport' that has virtual functions but non-virtual destructor [-Wdelete-non-virtual-dtor]
```
Fixes the following Clang 7 warnings and bugs:
```
editor/plugins/curve_editor_plugin.cpp:208:69: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]
editor/plugins/curve_editor_plugin.cpp:214:43: warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]
```
Changed according to @Zylann's suggestion on
https://github.com/godotengine/godot/pull/22593#discussion_r221699573
Fixes the following Clang 7 warnings:
```
drivers/gles3/rasterizer_scene_gles3.cpp:1260:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1280:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1281:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1282:10: warning: variable 'target' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
drivers/gles3/rasterizer_scene_gles3.cpp:1286:5: warning: variable 'target' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
editor/editor_properties_array_dict.cpp:982:15: warning: variable 'change_index' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
editor/editor_properties.cpp:2655:6: warning: variable 'lt' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
editor/settings_config_dialog.cpp:367:11: warning: variable 'current_search_box' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
```
Namely:
[-Wunneeded-internal-declaration]
[-Wunused-comparison]
[-Wunused-const-variable]
[-Wunused-function]
[-Wunused-private-fields]
Fixes the following Clang 7 warnings:
```
editor/plugins/script_editor_plugin.cpp:1417:20: warning: function '_find_node_with_script' is not needed and will not be emitted [-Wunneeded-internal-declaration]
editor/scene_tree_dock.cpp:1859:14: warning: function '_find_last_visible' is not needed and will not be emitted [-Wunneeded-internal-declaration]
modules/gdscript/gdscript_parser.cpp:7838:19: warning: equality comparison result unused [-Wunused-comparison]
scene/resources/mesh.cpp:549:35: warning: unused variable '_array_types' [-Wunused-const-variable]
scene/resources/mesh.cpp:563:18: warning: unused variable '_format_translate' [-Wunused-const-variable]
drivers/gles3/rasterizer_scene_gles3.cpp:54:28: warning: unused function 'store_transform2d' [-Wunused-function]
core/io/file_access_network.h:50:6: warning: private field 'ml' is not used [-Wunused-private-field]
core/io/file_access_zip.h:93:14: warning: private field 'archive' is not used [-Wunused-private-field]
core/io/resource_format_binary.h:122:6: warning: private field 'bin_meta_idx' is not used [-Wunused-private-field]
core/message_queue.h:47:9: warning: private field 'mutex' is not used [-Wunused-private-field]
main/tests/test_gui.cpp:63:11: warning: private field 'control' is not used [-Wunused-private-field]
modules/gdscript/gdscript_parser.h:558:7: warning: private field 'completion_static' is not used [-Wunused-private-field]
platform/x11/os_x11.h:148:11: warning: private field 'ip_unix' is not used [-Wunused-private-field]
platform/x11/os_x11.h:180:7: warning: private field 'net_wm_icon' is not used [-Wunused-private-field]
platform/x11/os_x11.h:189:6: warning: private field 'audio_driver_index' is not used [-Wunused-private-field]
platform/x11/os_x11.h:190:15: warning: private field 'capture_idle' is not used [-Wunused-private-field]
servers/physics/body_pair_sw.h:79:6: warning: private field 'cc' is not used [-Wunused-private-field]
servers/visual/visual_server_raster.h:62:7: warning: private field 'draw_extra_frame' is not used [-Wunused-private-field]
```
Fixes the following Clang 7 warnings:
```
core/object.cpp:44:1: warning: '_ObjectDebugLock' defined as a struct here but previously declared as a class [-Wmismatched-tags]
core/variant_call.cpp:43:1: warning: '_VariantCall' defined as a struct here but previously declared as a class [-Wmismatched-tags]
drivers/gles3/rasterizer_storage_gles3.h:765:2: warning: 'MultiMesh' defined as a struct here but previously declared as a class [-Wmismatched-tags]
editor/editor_node.h:794:1: warning: 'EditorProgress' defined as a struct here but previously declared as a class [-Wmismatched-tags]
modules/bullet/rigid_body_bullet.h:230:17: warning: class 'KinematicUtilities' was previously declared as a struct [-Wmismatched-tags]
modules/bullet/space_bullet.h:60:1: warning: class 'btSoftBodyWorldInfo' was previously declared as a struct [-Wmismatched-tags]
scene/resources/world_2d.cpp:40:1: warning: 'SpatialIndexer2D' defined as a struct here but previously declared as a class [-Wmismatched-tags]
scene/resources/world.cpp:39:1: warning: 'SpatialIndexer' defined as a struct here but previously declared as a class [-Wmismatched-tags]
servers/audio/reverb_sw.cpp:60:1: warning: 'ReverbParamsSW' defined as a struct here but previously declared as a class [-Wmismatched-tags]
thirdparty/bullet/BulletSoftBody/btSoftBody.h:43:1: warning: 'btSoftBodyWorldInfo' defined as a struct here but previously declared as a class [-Wmismatched-tags]
```
