Resource dimension APIs for textures

[hekota]

All buffer and textures have the GetDimensions method and we need to support this across the board. The list of tasks below focuses on adding the support for GetDimensions to textures. Buffer resources are handled here.

• Complete the mapping of GetDimensions overloads to builtin functions and LLVM intrinsic for textures (unless already completed in #346
• Add GetDimensions tests for textures to offload test suite
• Implement GetDimensions overloads for all texture resources