[9.16][CVE-2023-2828] Add test for dns_rbtdb overmem purging
Backport of !8141 (merged)
Closes #4055 (closed)
failing reproducer on affected v9.16: https://gitlab.isc.org/isc-projects/bind9/-/pipelines/143680
Backport of !8141 (merged)
Closes #4055 (closed)
failing reproducer on affected v9.16: https://gitlab.isc.org/isc-projects/bind9/-/pipelines/143680