Implement Vector4, Vector4i, Projection

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.

servers/rendering/renderer_canvas_render.h

@@ -77,7 +77,7 @@ public:
 		Rect2 rect_cache;
 		Transform2D xform_cache;
 		float radius_cache; //used for shadow far plane
-		//CameraMatrix shadow_matrix_cache;
+		//Projection shadow_matrix_cache;
 
 		Transform2D light_shader_xform;
 		//Vector2 light_shader_pos;