[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. Do you think that should be done before this PR gets merged?


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