[clang] [HLSL][RootSignature] Implement Lexing of DescriptorTables (PR #122981)

[Chris B via cfe-commits]

================
@@ -0,0 +1,124 @@
+//===--- HLSLRootSignature.def - Tokens and Enum Database -------*- C++ -*-===//
+
+//
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llvm-beanz wrote:

nit:
```suggestion
//
```

https://github.com/llvm/llvm-project/pull/122981