drop libknot <=3.2.x support
The 3.0.x part was cherry-picked from !1558 (merged)
It additionally drops 3.1, 3.2, and updates kres-gen-32.lua
to kres-gen-33.lua
accordingly.
In CI, pkgtests
for Debian 11 and 12 were updated so that they use upstream pkg.labs.nic.cz
repos, because those distro repos do not contain Knot DNS >=3.3. Sanity checks for old Knots were also dropped from CI.