[HLSL][SPIRV] `llvm.spv.resource.getdimensions.x` lowering

SPIR-V backed needs to handle the ``llvm.spv.resource.getdimensions.x`` intrinsic that was added in https://github.com/llvm/llvm-project/pull/161753. 
It is used by GetDimensions method on buffer resources (added in https://github.com/llvm/llvm-project/pull/161929).

Related proposal: https://github.com/llvm/wg-hlsl/blob/main/proposals/0033-resources-get-dimensions.md
