[clang] [analyzer] Limit `isTainted()` by skipping complicated symbols (PR #105493)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

The change LGTM overall, I support this kind of mitigation.

I added several cosmetic bikeshedding remarks as inline comments, but they are not important enough to block this PR.

https://github.com/llvm/llvm-project/pull/105493