This change implements dynamic loading of the OpenXR Loader library
on Android. If an OpenXR Loader library is not found,
Godot will still function with OpenXR disabled.
Also, on every platform, the OpenXR symbols are resolved at runtime
using xrGetInstanceProcAddr.
On Windows and Linux the OpenXR loader is included in the main
engine binary.
On Android, the OpenXR Loader is not built with the engine. Separately
distributed Android plugins will be provided with the correct loader
library for each device.
Co-authored-by: Gábor Pál Korom <gabor.p.korom@migeran.com>
Co-authored-by: Gábor Koncz <gabor.koncz@migeran.com>
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.
