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

[Victor Chernyakin via cfe-commits]

localspook wrote:

This feels like a gray area: is a performance change a "functional" change? [LLVM docs](https://llvm.org/docs/Lexicon.html#n) define NFC as "pure refactoring/cleanup", so it seems this isn't NFC, but it would be nice if it was more explicit

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