expand <type_traits> and <concepts>

[ZERICO2005]

Changes:

• expanded <type_traits>
• added to <concepts>
• added C++23 std::unreachable to <utility>

I have added to <type_traits> by replacing __has_feature(is_foo) to __has_builtin(__is_foo). From this, almost all of C++17 <type_traits> has been implemented except for:

/* C++11 */
common_type
aligned_storage
aligned_union
result_of
is_trivially_copy_assignable
is_trivially_move_assignable
make_signed
make_unsigned
is_destructable // works in C++20, requires Clang 16 to work in C++11
is_nothrow_destructable // works in C++20, requires Clang 16 to work in C++11
/* C++17 */
is_swappable
is_nothrow_swappable
invoke_result

I also replaced existing functions in <type_traits> with builtins if possible. I still need to do testing to ensure that all transformations are correct.

__has_builtin is the same as __has_feature, except that the latter is "deprecated", so it won't return true for newer builtins https://releases.llvm.org/15.0.0/tools/clang/docs/LanguageExtensions.html#builtin-functions

There are multiple ways to detect support for a type trait __X in the compiler, depending on the oldest version of Clang you wish to support.
* From Clang 10 onwards, __has_builtin(__X) can be used.
* From Clang 6 onwards, !__is_identifier(__X) can be used.
* From Clang 3 onwards, __has_feature(X) can be used, but only supports the following traits: