[CVE-2023-2828] Add test for dns_rbtdb overmem purging
Add a unit test to check if the overmem purging in the RBTDB is effective when mixed size RR data is inserted into the database.
Co-authored-by: Ondřej Surý ondrej@isc.org Co-authored-by: Jinmei Tatuya jtatuya@infoblox.com
Closes #4055 (closed)
failing reproducer on affected 9.19: https://gitlab.isc.org/isc-projects/bind9/-/pipelines/143645