* Automatically selects the newly created directory
* Automatically selects "res://" when nothing is selected
* Fixes an error when overwrite/replace dialog appears
* Changes "copy checkbox + action button" to "copy button + move button"
* Double clicking a directory (un)collapses it instead of copy/move
* Uses DirectoryCreateDialog for "Create Folder"
Also start organizing editor-specific GUI components
into a dedicated folder, `editor/gui`.
Also move `editor_file_server` next to the rest of debugger classes.
