libstdc++: [_GLIBCXX_DEBUG] Complete deadlock fix on safe iterators [PR108288]

libstdc++: [_GLIBCXX_DEBUG] Complete deadlock fix on safe iterators [PR108288]

Complete fix on all _Safe_iterator post-increment and post-decrement implementations
and on _Safe_local_iterator.

libstdc++-v3/ChangeLog:

	PR libstdc++/108288
	* include/debug/safe_iterator.h (_Safe_iterator<>::operator++(int)): Extend deadlock
	fix to other iterator category.
	(_Safe_iterator<>::operator--(int)): Likewise.
	* include/debug/safe_local_iterator.h (_Safe_local_iterator<>::operator++(int)):
	Fix deadlock.
	* testsuite/util/debug/unordered_checks.h (invalid_local_iterator_pre_increment): New.
	(invalid_local_iterator_post_increment): New.
	* testsuite/23_containers/unordered_map/debug/invalid_local_iterator_post_increment_neg.cc:
	New test.
	* testsuite/23_containers/unordered_map/debug/invalid_local_iterator_pre_increment_neg.cc:
	New test.