[llvm] [ctx_prof] Factor the callsite instrumentation exclusion criteria (PR #108471)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

> > Reusing this in the logic fetching the instrumentation in `CtxProfAnalysis`
> 
> Do you mean it will be reused in a future patch? Because I only see the one use here.

yes

https://github.com/llvm/llvm-project/pull/108471