[clang-tools-extra] [clang-tidy] Support find for string-like classes in readability-container-contains (PR #157243)

[Victor Chernyakin via cfe-commits]

localspook wrote:

It looks like the check could be extended quite easily to support `cend`, not just `end`. (I’m not advocating doing that in *this* PR, but I noticed it and want to note it down)

https://github.com/llvm/llvm-project/pull/157243