Add an additional class of names to adb

When using static-stub zones where the servers are specified by addresses, the <zonename,address> pairs get mixed with <name,address> pairs from other sources. This can lead to static zone queries being sent to addresses not specified in the configuration and/or the <zonename,address> from the static-stub zone being used instead of the actual addresses associated with the name. See the staticstub tests in https://gitlab.isc.org/isc-projects/bind9/-/pipelines/190390 for examples of this. Add a third class of names to adb and use it for the <zonename,address> pairs produced by static-stub zones.