[BE]: Enable clang-tidy check for readability-string-compare (#115994)

Adds a clang-tidy check to ensure string compare is not used unnecessarily in a way that is less efficient and less readable if an equality overload exists.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/115994
Approved by: https://github.com/albanD

.clang-tidy

@@ -52,6 +52,7 @@ modernize-*,
 -modernize-use-nodiscard,
 performance-*,
 readability-container-size-empty,
+readability-string-compare,
 '
 HeaderFilterRegex: '^(aten/|c10/|torch/).*$'
 AnalyzeTemporaryDtors: false