This patch removes all of the frozen headers which don't provide
anything. Basically any header that's C++11-or-later is removed from the
frozen headers.

This is part of
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc.

This significantly reduces the amount of debug information generated
for codebases using libc++, without hurting the debugging experience.

This patch implements the forwarding to frozen C++03 headers as
discussed in
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. In the
RFC, we initially proposed selecting the right headers from the Clang
driver, however consensus seemed to steer towards handling this in the
library itself. This patch implements that direction.

At a high level, the changes basically amount to making each public
header look like this:

```
// inside <vector>
#ifdef _LIBCPP_CXX03_LANG
#  include <__cxx03/vector>
#else
  // normal <vector> content
#endif
```

In most cases, public headers are simple umbrella headers so there isn't
much code in the #else branch. In other cases, the #else branch contains
the actual implementation of the header.

Including The frozen C++03 headers results in a lot of formatting
changes in the main headers, so this splits these changes into a
separate commit instead.

This is part of
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc.

This makes libc++'s <filesystem> tests compatible with MSVC's STL.

In msvc_stdlib_force_include.h, we need to define 3 more macros:

- _CRT_DECLARE_NONSTDC_NAMES activates the POSIX names of
  `getcwd` etc. As the comment explains, we need this because
  we test with Clang `-fno-ms-compatibility`, which defines 
  `__STDC__` to `1`, which causes the UCRT headers to disable 
  the POSIX names by default.
- Then we need _CRT_NONSTDC_NO_WARNINGS to avoid emitting
  deprecation warnings about the POSIX names.
- Finally, we need `NOMINMAX` to seal away the ancient evil.

These macros are documented in https://learn.microsoft.com/en-us/cpp/c-runtime-library/compatibility?view=msvc-170.

As a drive-by change, the patch adds a "simulated" macro for 
__has_feature(hwaddress_sanitizer). It also clang-formats all
of msvc_stdlib_force_include.h and removes guards for
__has_builtin(__builtin_source_location) in <source_location>,
since those are not needed anymore.

AppleClang 1403 has some bugs that prevent std::source_location from
working properly on it. Consequently, we XFAILed the unit test for
source_location with that compiler. However, we should also avoid
advertising that the feature is supported on that compiler, otherwise
our feature-test macros lie. This was noticed to break Boost.Asio
when building with a recent libc++ and AppleClang 14.0.3.

rdar://106863087

Differential Revision: https://reviews.llvm.org/D146837

This requires the __builtin_source_location() builtin, as implemented
by GCC and Clang.

Fixes https://github.com/llvm/llvm-project/issues/56363

Differential Revision: https://reviews.llvm.org/D120634