libstdc++: Add @headerfile and @since to doxygen comments [PR40380]

libstdc++-v3/ChangeLog:

	PR libstdc++/40380
	* include/bits/basic_string.h: Improve doxygen comments.
	* include/bits/cow_string.h: Likewise.
	* include/bits/forward_list.h: Likewise.
	* include/bits/fs_dir.h: Likewise.
	* include/bits/fs_path.h: Likewise.
	* include/bits/quoted_string.h: Likewise.
	* include/bits/stl_bvector.h: Likewise.
	* include/bits/stl_map.h: Likewise.
	* include/bits/stl_multimap.h: Likewise.
	* include/bits/stl_multiset.h: Likewise.
	* include/bits/stl_set.h: Likewise.
	* include/bits/stl_vector.h: Likewise.
	* include/bits/unordered_map.h: Likewise.
	* include/bits/unordered_set.h: Likewise.
	* include/std/filesystem: Likewise.
	* include/std/iomanip: Likewise.