This PR introduces a TableGen-based code generation system for HLSL intrinsic overloads as described in proposal [[0043]](https://github.com/llvm/wg-hlsl/blob/main/proposals/0043-hlsl-intrinsic-tablegen.md) for replacing hand-written boilerplate with declarative .td definitions. Actual changes to `hlsl_intrinsics.h` and `hlsl_alias_intrinsics.h` to replace handwritten HLSL intrinsic overloads with TableGen is left to follow-up PRs. Assisted-by: GitHub Copilot (powered by Claude Opus 4.6)