[clang] [Clang] Resolved type of expression indexing into pack of values of a non-dependent type (PR #121405)

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TilakChad wrote:

Alternatively, we could've make the PackIndexingExpr to be type dependent and try to verify type compatibility lazily during instantiation. 
It is how MSVC and GCC seems to behave. 

Considering that the clang seems to be eager about such type compatibility, this changes is along the lines of how clang currently behaves. 

https://godbolt.org/z/v5v3vqY8W 

https://github.com/llvm/llvm-project/pull/121405