[9.20] fix: dev: Backport test for update-policy per-type max quota bypass via crafte...

An authenticated DDNS client could bypass update-policy per-type record limits
(e.g. TXT(3)) by including padding records in the UPDATE message that are
silently skipped during processing in the main branch.

As BIND 9.20 is not affected, only backport the test.

Closes #5799

Backport of MR !11708

Merge branch 'backport-5799-fix-counter-desync-in-SSU-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11760