[clang] [analyzer] Avoid unnecessary super region invalidation in `CStringChecker` (PR #146212)

[via cfe-commits]

flovent wrote:

> Also please follow the [Coding Standard](https://llvm.org/docs/CodingStandards.html#name-types-functions-variables-and-enumerators-properly) and use `UpperCamelCase` variables for variables (including ones that store lambda functions), while `lowerCamelCase` is for methods. Of course, it is also right to follow the "local customs" of older code fragments, but I'd suggest gradually transitioning to the global standard by following the coding standard for the freshly added variables and perhaps transitioning the variables which are mostly used in the code that you edit.

I totally agree using new standard in new code, i think i didn't notice that because i  basiclly copy the orginal code to here and clangd doesn't give warning about clang-tidy's `readability-identifier-naming` check (just found out it's disabled in clang folder), will check that manually next time.

https://github.com/llvm/llvm-project/pull/146212