chg: usr: Cap glue records cached from a referral

named cached every glue record from a referral, retaining far more
than resolution will ever use.  The number of nameservers and
addresses kept per referral is now bounded in the delegation database.

Closes #5701

Merge branch '5701-limit-the-number-of-GLUE-records' into 'main'

See merge request isc-projects/bind9!11970