fix: usr: CDS/CDNSKEY records were not removed when re-configuring the server

When on an ``rndc reconfig`` the DNSSEC policy changes such that it changes the expected ``CDNSKEY`` and/or ``CDS`` records in the zone, the RRset should
be updated accordingly. This did not happen when removing digests from the configuration, or setting `cdnskey no;`. This has been fixed.

Closes #6166

Merge branch '6166-reconfig-delete-cds' into 'main'

See merge request isc-projects/bind9!12265