[clang] [llvm] [HLSL] Disallow named struct types as parameters in target extension types (PR #115971)

[Justin Bogner via cfe-commits]

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bogner wrote:

This isn't testing the AST, so it shouldn't be in the `test/AST` folder. In any case, I think there's sufficient coverage by the changes to the `CodeGenHLSL/builtins` tests and `TypesTest`, so this one can probably just be removed.

https://github.com/llvm/llvm-project/pull/115971