fix: dev: minimize zone hooktable lookups

Merging !10483 caused a performance regression because the zone hooktable had to be looked up every time a hook point was reached, even if no zone plugins were configured. We now look up the zone hooktable when a zone is attached to the query context, and keep a pointer to it until the qctx is destroyed.

Merge branch 'each-zoneplugin-zonehook-once' into 'main'

See merge request isc-projects/bind9!10959