[clang] [Clang][Sema] Use the correct lookup context when building overloaded 'operator->' in the current instantiation (PR #104458)

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cor3ntin wrote:

> @cor3ntin After giving it another look, I think the existing tests are sufficient (the tests updated by this PR were written by me to test this exact scenario). WDYT?

I think the tests you have are fine

https://github.com/llvm/llvm-project/pull/104458