[clang][CodeGen] Guard ubsan checks with `llvm.allow.ubsan.check` (#87436)

Intrinsic inserted into CodeGenFunction::EmitCheck, which
is not mostly used by CFI.

CFI is not the goal, and fixing inconsistencies with CFI is outside of
the cope of the patch.

RFC:
https://discourse.llvm.org/t/rfc-add-llvm-experimental-hot-intrinsic-or-llvm-hot/77641