Resolver is parent-centric

Resolver is parent-centric

The resolver now uses glue addresses from `dns_deleg_t` objects stored
in the delegation database.  The main cache is still used for ADB A/AAAA
lookups when no glue is available for a nameserver name.

The resolver's `fctx_getaddresses()` is refactored to, for each
delegation of the delegation set, try to get the address-based finds,
then nameserver name lookups. (Later, the logic to handle DELEG
`include-delegparm=` will be hooked there too.)