[clang] [analyzer] Fix performance of getTaintedSymbolsImpl() (PR #89606)

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

> @Xazax-hun WDYT?

If it really takes over an hour to analyze a file in clang-18, I'd agree that this has similar severity to a crash, and I support backporting the fix. 

https://github.com/llvm/llvm-project/pull/89606