[HLSL][RootSignature] Allow for multiple parsing errors in `RootSignatureParser`

[inbelic]

At the moment, the RootSignatureParser will early exit when it encounters it's first error. To be more in line with Clang error parsing, and to hopefully reduce the number of compile cycles for users, we can modify the parser to continue looking for parsing errors even after we encounter the first one.

For this to be ready for refinement, we should answer the question of what granularity we can do so.
It seems fairly straightforward at the granularity of a RootElement (RootConstants, CBV, StaticSampler, etc.), but we can see how complex it might be to make that granularity smaller.

AC:

• HLSLRootSignatureParser is updated to allow for reporting multiple parsing errors at a given granularity