Add more self-tests for 'hash_map' with Value type with non-trivial constructor/destructor

... to document the current behavior.

	gcc/
	* hash-map-tests.c (test_map_of_type_with_ctor_and_dtor): Extend.
	(test_map_of_type_with_ctor_and_dtor_expand): Add function.
	(hash_map_tests_c_tests): Call it.