libstdc++: Use memchr to optimize std::find [PR88545]

This optimizes std::find to use memchr when searching for an integer in
a range of bytes.

libstdc++-v3/ChangeLog:

	PR libstdc++/88545
	PR libstdc++/115040
	* include/bits/cpp_type_traits.h (__can_use_memchr_for_find):
	New variable template.
	* include/bits/ranges_util.h (__find_fn): Use memchr when
	possible.
	* include/bits/stl_algo.h (find): Likewise.
	* testsuite/25_algorithms/find/bytes.cc: New test.