System test for nxdomain-redirect combined with dns64

System test for nxdomain-redirect combined with dns64

An AAAA query for a non-existent name into a view that combines
nxdomain-redirect with dns64 used to abort named via the DNS64
fallback in query_nodata(). The new module exercises all three
documented entry paths into query_redirect(): the authoritative
NXDOMAIN path (ns7, tripping INSIST(!is_zone) in
query_notfound()), the recursive NCACHENXRRSET path (ns8,
tripping REQUIRE in dns_rdataset_first() on a disassociated
rdataset), and the synth-from-dnssec path (ns10 validating
against ns9's signed root, with a primer A query so the second
AAAA reaches query_redirect() via query_coveringnsec()). ns9
serves as a neutral upstream so the cached and synthesized
negatives land real NXRRSETs.

Assisted-by: Claude:claude-opus-4-7
(cherry picked from commit 739a067de89834820372ae14171c0889f7aedc83)