The call chain to `Mutex:lock` can be polluted by stack protector. For
completely safe, let's postpone the main TLS tearing down to a separate
phase.
fix#108030
- added at_quick_exit function
- used helper file exit_handler which reuses code from atexit
- atexit now calls helper functions from exit_handler
- test cases and dependencies are added
---------
Co-authored-by: Aaryan Shukla <aaryanshukla@google.com>
- In /libc/src/__support/ OSUtil, changed quick_exit to just exit, and
put in namespace
LIBC_NAMESPACE::internal.
- In /libc/src/stdlib added quick_exit
- Added test files for quick_exit
