[9.18] fix: dev: Do not cache signatures for rejected data

The cache has been updated so that if new data is rejected - for example, because there was already existing data at a higher trust level - then its covering RRSIG will also be rejected.

Closes #5132

Backport of MR !9999

Merge branch 'backport-5132-improve-cd-behavior-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!10135