[clang] [Clang] Implement CWG3005 Function parameters should never be name-independent (PR #138245)

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cor3ntin wrote:

> THIS example should also be ill-formed by CWG3005:
> 
> ```
> 
> struct S3 {
>    union {
>      int _;
>      };
>     int _; // error, the one in the union isn't type independent
> };
> ```

This is CWG2764 - I'll do that in a separate PR (and I need to open another issue because I think the wording fails to implement the intent) 

https://github.com/llvm/llvm-project/pull/138245