Add tests for RWTexture2D

[Icohedron]

References

• https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-object-rwtexture2d

Tasks

• Add RWTexture2D to offload-test-suite ResourceKind

  • Note: RWTexture2D already exists in the offload-test-suite ResourceKind enum — verify it works with the new front-end type

• Write tests (offload-test-suite/test/Feature/Textures/)

  • RWTexture2D.OperatorIndex.test.yaml — read and write via operator[]