[clang-tools-extra] [clang-tidy] Speed up `readability-container-contains` (PR #175121)

[Victor Chernyakin via cfe-commits]

localspook wrote:

> And If you instantiate the function, it works with the template.

This PR breaks that case, true. But I hope we can agree that the current behaviour is still not ideal, right? We would like the check to work whether you instantiate the template or not. That would require another PR implementing heuristic name resolution (and I would be happy to write it!).

> Maybe we can change traversal kind later?

I think it would be less work in the end to implement the heuristic, then come back to this PR: does that sound like a plan?


https://github.com/llvm/llvm-project/pull/175121