[clang] [Clang] [Sema] Handle placeholders in '.*' expressions (PR #83103)

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llvmbot wrote:

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Failed to cherry-pick: https://github.com/Sirraide/llvm-project/commit/74fa05dead4d52eef3c33406d05dd1bbaf10d546

https://github.com/llvm/llvm-project/actions/runs/8147057328

Please manually backport the fix and push it to your github fork.  Once this is done, please create a [pull request](https://github.com/llvm/llvm-project/compare)

https://github.com/llvm/llvm-project/pull/83103