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

Fix #109327. Small parts taken from #110351.

Removed the type checking between `contains` and `count`/`find`
arguments for simplicity. Because of overloads, this type-checking is
tricky. The same strategy is used in `modernize-use-starts-ends-with`.

Co-authored-by: dl8sd11 <gcchen@google.com>
GitOrigin-RevId: 5c21b1b6dcc808795d1596ea2e29f94314488026
5 files changed