core: Use macros to generate ao2_container callbacks where possible.

This uses AO2_STRING_FIELD_HASH_FN and AO2_STRING_FIELD_CMP_FN where
possible in the Asterisk core.

This removes CMP_STOP from the result of CMP_FN callbacks for the
following structure types:
* ast_bucket_metadata
* ast_bucket_scheme
* generic_monitor_instance_list (ccss.c)
* ast_bucket_file (media_cache.c)
* named_acl

Change-Id: Ide4c1449a894bce70dea1fef664dade9b57578f1