[LICM] Generalize unwinding check during scalar promotion

This extract a common isNotVisibleOnUnwind() helper into
AliasAnalysis, which handles allocas, byval arguments and noalias
calls. After D116998 this could also handle sret arguments. We
have similar logic in DSE and MemCpyOpt, which will be switched
to use this helper as well.

The noalias call case is a bit different from the others, because
it also requires that the object is not captured. The caller is
responsible for doing the appropriate check.

Differential Revision: https://reviews.llvm.org/D117000