[clang] [llvm] [HLSL] Generate semantic signature metadata (PR #212892)

[Finn Plummer via cfe-commits]

inbelic wrote:

Build failures are caused by myself missing a build dependency on `DXILResource.h` and this commit will be reverted/relanded: https://github.com/llvm/llvm-project/pull/215844

https://github.com/llvm/llvm-project/pull/212892