Implement built-in classes Vector4, Vector4i and Projection.
* Two versions of Vector4 (float and integer).
* A Projection class, which is a 4x4 matrix specialized in projection types.
These types have been requested for a long time, but given they were very corner case they were not added before.
Because in Godot 4, reimplementing parts of the rendering engine is now possible, access to these types (heavily used by the rendering code) becomes a necessity.
**Q**: Why Projection and not Matrix4?
**A**: Godot does not use Matrix2, Matrix3, Matrix4x3, etc. naming convention because, within the engine, these types always have a *purpose*. As such, Godot names them: Transform2D, Transform3D or Basis. In this case, this 4x4 matrix is _always_ used as a _Projection_, hence the naming.
Now the `linuxbsd` platform can be built headlessly (e.g. without X11
development libraries).
I also cleaned up some weird (old?) usages of the `env` variable which
seem to make no difference and are used nowhere else.
* Map is unnecessary and inefficient in almost every case.
* Replaced by the new HashMap.
* Renamed Map to RBMap and Set to RBSet for cases that still make sense
(order matters) but use is discouraged.
There were very few cases where replacing by HashMap was undesired because
keeping the key order was intended.
I tried to keep those (as RBMap) as much as possible, but might have missed
some. Review appreciated!
* Changed to use the same stages as extensions.
* Makes the initialization more coherent, helping solve problems due to lack of stages.
* Makes it easier to port between module and extension.
* removed the DRIVER initialization level (no longer needed).
Didn't commit all the changes where it wants to initialize a struct
with `{}`. Should be reviewed in a separate PR.
Option `IgnoreArrays` enabled for now to be conservative, can be
disabled to see if it proposes more useful changes.
Also fixed manually a handful of other missing initializations / moved
some from constructors.
Convert method signature parameters to const where it is possible
# Conflicts:
# drivers/gles3/rasterizer_canvas_gles3.cpp
# drivers/gles3/rasterizer_canvas_gles3.h
# editor/plugins/animation_state_machine_editor.cpp
# editor/plugins/animation_state_machine_editor.h
