[HLSL] Implement `GetDimensions` methods for buffer resources

[hekota]

Implement GetDimensions methods on all buffer resources based on proposal llvm/wg-hlsl#346.

• Introduce Clang builtin function(s) based on the proposal.
• Lower the builtin calls to llvm.dx.resource.getdimensions and read the arguments back.
• Implement GetDimensions methods for buffers in HLSLBuildinTypeDeclBuilder and add them to all resource buffers

Applieds to:

StructuredBuffer
RWStructuredBuffer
RasterizerOrderedStructuredBuffer
AppendStructuredBuffer
ConsumeStructuredBuffer
RWBuffer
ByteAddressBuffer
{RW}ByteAddressBuffer

Docs:
https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-object-structuredbuffer-getdimensions
https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-object-rwbuffer-getdimensions
https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-object-rwbyteaddressbuffer-getdimensions

Example:
https://godbolt.org/z/bz7zxsf5n

Depends on: #112982

[bogner]

Note that the GetDimensions DXIL op interprets its arguments differently depending on the type of resource. We should consider whether we're okay mimicking that in our llvm intrinsic representations or if we want to implement a more strongly typed set of intrinsics until we lower to the dxil op.

[tex3d]

Note that the GetDimensions DXIL op interprets its arguments differently depending on the type of resource. We should consider whether we're okay mimicking that in our llvm intrinsic representations or if we want to implement a more strongly typed set of intrinsics until we lower to the dxil op.

I think we need different builtins for the different output arguments depending on resource type (like structuredbuffer vs. textures, and uint vs. float outputs), then in CGBuiltin we use a single intrinsic function returning a struct of 4 int32s that will map to the final DXIL op directly for easy lowering.