[HLSL] Generate remaining Root Signature element Metadata from AST

[inbelic]

This issue handles the generation of root signature LLVM IR metadata from the parsed AST for the remaining root element types.

The infrastructure will have been previously defined in #126584, so this issue simply requires defining the metadata emission in HLSLRootSignature.h.

This is dependent on the definition of all root elements when #120472 is completed.

AC:

• Implement metadata generation for remaining RootElement types
• Add tests of generated metadata using emit-llvm in CodeGenHLSL/RootSignatures.hlsl

[inbelic]

This was pre-maturely closed and is re-opened to be correctly tracked here: #142642.