[clang] [clang][analyzer] Simplify code of StreamChecker (NFC). (PR #79312)

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NagyDonat wrote:

I'm seconding the suggestions of @steakhal, and in particular I agree with
> I'd also advise against using more callables bundled with CallDescriptions. They make debugging code more difficult, as the control-flow would become also data-dependent. I'd suggest other ways to generalize.

Instead of creating this shared framework that calls different callbacks depending on the checked function, consider keeping separate top-level evaluator functions that rely on a shared set of smaller tool-like helper functions.

https://github.com/llvm/llvm-project/pull/79312