[clang] Skip over std namespace in WebKit checkers. (PR #90552)

[Artem Dergachev via cfe-commits]

haoNoQ wrote:

Hmm it doesn't look like we actually have that other suppression. It looks like the checker simply never warned in the standard library because there aren't WebKit classes in the standard library. But it looks like you've found a few cases where it actually happens? How does this happen? Is this because templates get instantiated with WTF classes as type arguments? Maybe a something completely different solution should be considered?

If we think it's actually a good idea to suppress warnings about standard functions, typically these suppressions are implemented with `getSourceManager().isInSystemHeader(SLoc)` checks, such as [the one we actually have](https://github.com/llvm/llvm-project/blob/llvmorg-19-init/clang/lib/StaticAnalyzer/Checkers/WebKit/NoUncountedMembersChecker.cpp#L110). This covers not only the standard library, but also other code outside of your project (basically everything that goes with `-isystem` as opposed to `-I`). Which may or may not be what we want.

I think it's likely that your solution is optimal but I still want to see some examples to understand what exactly we're dealing with.

https://github.com/llvm/llvm-project/pull/90552