Merge "exitcode" flag from ASan, LSan, TSan and "exit_code" from MSan
into one entity. Additionally, make sure sanitizer_common now uses the
value of common_flags()->exit_code when dying on error, so that this
flag will automatically work for other sanitizers (UBSan and DFSan) as
well.
- User-visible changes ***
- "exit_code" MSan runtime flag is removed in favor of "exitcode"
- asan_set_error_exit_code() and msan_set_exit_code() functions are removed. With few exceptions, we don't support changing runtime flags during program execution - we can't make them thread-safe. The users should use __sanitizer_set_death_callback() that would call _exit() with proper exit code instead.
- Plugin tools (LSan and UBSan) now inherit the exit code of the parent tool. In particular, this means that ASan would now crash the program with exit code "1" instead of "23" if it detects leaks.