We can now use object and other modes on top of Cycles.
Since we are now always on "render_to_view" (old Rendered mode), the
pause button is always visible.
- Unify GPUMaterial creation (world/mesh).
- Support for multiple shader variations (not used for now).
- Convert GPUInputs to DRWUniforms to be used with the draw manager.
- Nodetree Update is not supported. The only way to refresh the shaders is to change render engine.
- Cleanup in GPUPass.
- Add new temporary Node Compatibility type. Compatibility types should be removed in the future.
- use DRW_engine prefix for engine types.
- use engine suffix for files that define a draw engine.
- remove engines from include path (they're only referenced once)
