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

Summary:
This file is an object library, but uses the `LIBC_COPT_PUBLIC_PACKAING`
option. This will always be undefined which leads to a type mismatch
when uses actually try to link against it. This patch simply removes
this and turns it into a header only library. This means that the
implementations of the callback lists and the mutexes need to live in
their respective files. The result is that `atexit` needs to be defined
for `at_quick_exit` to be valid.

This is a part of #97655.

Reverts llvm/llvm-project#98075

bots are broken

This is a part of #97655.

- 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>

This PR address issue #89002.

#### Changes in this PR

* Added a simple implementation of `cpp::lock_guard` (an equivalent of
`std::lock_guard`) in libc/src/__support/CPP inspired by the libstdc++
implementation
* Added tests for `cpp::lock_guard` in
/libc/test/src/__support/CPP/mutex_test.cpp
* Replaced all references to `MutexLock` with `cpp::lock_guard`

---------

Co-authored-by: Guillaume Chatelet <gchatelet@google.com>

I'm trying to break up the pieces of supporting __cxa_finalize into smaller
commits. Provide this symbol first, and make use of it from exit.

Next will be to store __dso_handle, then finally to only run callbacks that
were registered from a specific dso.

Link: #85651
Link: https://itanium-cxx-abi.github.io/cxx-abi/abi.html#dso-dtor

The cpp namespace should only be used to mirror APIs from C++'s std::
namespace
(at least until we share more code with libc++, see

https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701)