fix: usr: Fix dnssec-keygen key collision checking for KEY rrtype keys

The :iscman:`dnssec-keygen` utility program failed to detect
possible Key ID collisions with the existing keys generated
using the non-default ``-T KEY`` option (e.g. for ``SIG(0)``).
This has been fixed.

Closes #5506

Merge branch '5506-dnssec-keygen-sig0-keys-collision-fix' into 'main'

See merge request isc-projects/bind9!11047