libstdc++: "safe" in several library names is misleading (LWG 3379)

libstdc++: "safe" in several library names is misleading (LWG 3379)

	* include/bits/range_access.h (enable_safe_range): Rename to
	enable_borrowed_range.
	(__detail::__maybe_safe_range): Rename to __maybe_borrowed_range.
	(safe_range): Rename to borrowed_range.
	* include/bits/ranges_algo.h: Adjust to use new names.
	* include/bits/ranges_algobase.h: Likewise.
	* include/bits/ranges_uninitialized.h: Likewise.
	* include/std/ranges: Likewise.
	(safe_iterator_t): Rename to borrowed_iterator_t.
	(safe_subrange_t): Rename to borrowed_subrange_t.
	* include/std/span: Adjust to use new names.
	* include/std/string_view: Likewise.
	* include/experimental/string_view: Likewise.
	* testsuite/std/ranges/access/begin.cc: Likewise.
	* testsuite/std/ranges/access/cbegin.cc: Likewise.
	* testsuite/std/ranges/access/cdata.cc: Likewise.
	* testsuite/std/ranges/access/cend.cc: Likewise.
	* testsuite/std/ranges/access/crbegin.cc: Likewise.
	* testsuite/std/ranges/access/crend.cc: Likewise.
	* testsuite/std/ranges/access/data.cc: Likewise.
	* testsuite/std/ranges/access/end.cc: Likewise.
	* testsuite/std/ranges/access/rbegin.cc: Likewise.
	* testsuite/std/ranges/access/rend.cc: Likewise.
	* testsuite/std/ranges/safe_range.cc: Likewise.
	* testsuite/std/ranges/safe_range_types.cc: Likewise.
	* testsuite/util/testsuite_iterators.h: Likewise.