[clang-tools-extra] [clang-tidy] Add readability-string-view-substr check (PR #120055)

[Piotr Zegar via cfe-commits]

https://github.com/PiotrZSL requested changes to this pull request.

Should be readability-stringview-substr
There are already 2 other checks that use "stringview" instead of "string-view".

https://github.com/llvm/llvm-project/pull/120055