Blender Git Loki

GPUTexture: GL Backend Isolation

This is a massive cleanup needed for vulkan support T68990. It provides:

- More meaningful enums with conversion functions.
- Less hacky supports of arrays and cubemaps (all considered layered).
- More inline with the stateless design of vulkan and modern GL.
- Methods Fallbacks are using framebuffer functions that are wrapped
instead of implementing inside the texture module.

What is not in there:
- API change.
- Samplers support (breaks a few effects).

GPUFramebuffer: Encapsulate single attachement clear

This is in preparation of using it to clear single texture.

Also includes minor cleanups about not using tex target in
assert and adding enum operators.

Cleanup: EEVEE: Use correct array size and use equals_v2v2_int

GPUTexture: Add skeleton of the new GLTexture class

GPUTexture: Remove bind to edit calls

This is going to be unecessary after the GPU opengl texture backend refactor.

For now add a save/restore mechanism to leave the state untouched.

Also remove some calls where the caller would bind to particular binding
point and set the shader uniform.