[clang] [NFC][HLSL] Move Sema work from `ParseMicrosoftRootSignatureAttributeArgs` (PR #143184)

[Helena Kotas via cfe-commits]

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@@ -4942,18 +4942,13 @@ void Parser::ParseMicrosoftRootSignatureAttributeArgs(ParsedAttributes &Attrs) {
 
   // Construct our identifier
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hekota wrote:

Not really related to this change, I just noticed the `ParseMicrosoftRootSignatureAttributeArgs` name. Would `ParseHLSLRootSignatureAttributeArgs` be a better fit?

https://github.com/llvm/llvm-project/pull/143184