Fix false positive leak reported by GCC ASAN (#9816)

Leak found by the corrupt-dump-fuzzer when using GCC ASAN, which seems
to falsely report leaks on pointers kept only on the stack when calling exit.
Instead we now use _exit on panic / assert to skip these leak checks.

Additionally, check for sanitizer warnings in the corrupt-dump-fuzzer between iterations,
so that when something is found we know which test to relate it too (and it prints reproduction command list)