[DirectX backend] Add analysis to collect DXILResources

Now only DXILTranslateMetadata uses DXILResources, so DXILResourceWrapper is only used by DXILTranslateMetadata.
Once we add lower for createHandle, DXILResourceWrapper will be used in more passes.
Also we can add resource index allocation in DXILResourceWrapper.

Reviewed By: beanz

Differential Revision: https://reviews.llvm.org/D135190