* Apply the typo fix as a separate NFC patch from here:
https://github.com/llvm/llvm-project/pull/134330/files#r2313015079

Fixes #128658

The need for `_LIBCPP_TEMPLATE_VIS` has been removed in #133233.

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

This makes the placement of the attribute more consistent. This also
avoids clang dropping the attribute silently (see #120722).

This patch adds a large number of missing includes in the libc++ headers
and the test suite. Those were found as part of the effort to move
towards a mostly monolithic top-level std module.

Many headers include `<cstddef>` just for size_t, and pulling in
additional content (e.g. the traits used for std::byte) is unnecessary.
To solve this problem, this patch splits up `<cstddef>` into
subcomponents so that headers can include only the parts that they
actually require.

This has the added benefit of making the modules build a lot stricter
with respect to IWYU, and also providing a canonical location where we
define `std::size_t` and friends (which were previously defined in
multiple headers like `<cstddef>` and `<ctime>`).

After this patch, there's still many places in the codebase where we
include `<cstddef>` when `<__cstddef/size_t.h>` would be sufficient.
This patch focuses on removing `<cstddef>` includes from __type_traits
to make these headers non-circular with `<cstddef>`. Additional
refactorings can be tackled separately.