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

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Sirraide wrote:

Lastly, it also seems weird to me that a function called `CreateOverloadedBinOp()` is called to handle `.*`—an operator that can’t be overloaded—but seeing as this function has apparently been handling this case for over a decade now, I’m probably not going to question this any further.

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