fix: test: Fix 'ans' servers so they respond with consistent answers to NS queries...

fix: test: Fix 'ans' servers so they respond with consistent answers to NS queries at QNAME.

The ANS servers were not to written to handle NS queries at the QNAME, resulting in gratuitous protocol errors that will break tests when NS requests are made for the QNAME: i.e., NXDOMAIN for NS vs data for expected type,  CNAME not being returned for all query types.

Prerequisite for !9155

Closes #5062

Merge branch '5062-fix-ans-servers-ns-at-qname' into 'main'

See merge request isc-projects/bind9!9786