libstdc++: Optimize std::try_facet and std::use_facet [PR103755]

libstdc++: Optimize std::try_facet and std::use_facet [PR103755]

The std::try_facet and std::use_facet functions were optimized in
r13-3888-gb3ac43a3c05744 to avoid redundant checking for all facets that
are required to always be present in every locale.

This performs a simpler version of the optimization that only applies to
std::ctype<char>, std::num_get<char>, std::num_put<char>, and the
wchar_t specializations of those facets. Those are the facets that are
cached by std::basic_ios, which means they're used on construction for
every iostream object. This smaller change is suitable for the gcc-12
branch, and mitigates the performance loss for powerpc64le-linux on the
gcc-12 branch caused by r12-9454-g24cf9f4c6f45f7 for PR 103387. It also
greatly improves the performance of constructing iostreams objects, for
all targets.

libstdc++-v3/ChangeLog:

	PR libstdc++/103755
	* include/bits/locale_classes.tcc (try_facet, use_facet): Do not
	check array index or dynamic type when accessing required
	specializations of std::ctype, std::num_get, or std::num_put.
	* testsuite/22_locale/ctype/is/string/89728_neg.cc: Adjust
	expected errors.