[Sanitizer] Fix sanitizer tests without reducing optimization levels

As discussed, these tests are compiled with optimization to mimic real
sanitizer usage [1].

Let's mark relevant functions with `noinline` so we can continue to
check against the stack traces in the report.

[1] https://reviews.llvm.org/D96198

This reverts commit 04af72c5.

Differential Revision: https://reviews.llvm.org/D96357