Disable UPDATE and NOTIFY for non-IN classes

Disable UPDATE and NOTIFY for non-IN classes

Return NOTIMP for UPDATE and NOTIFY requests received for views with a
class other than IN.  Only QUERY is now supported for non-IN views such
as CHAOS.

When running dns dns_rdata_tostruct() with types that are only defined
for class IN, ensure that the class is correct before proceeding.

Add an assertion that any zone being updated is of class IN. (Note
that previously, a DLZ zone could have its class value set incorrectly
to NONE; this has been fixed.)

This addresses YWH-PGM40640-70 and YWH-PGM40640-73 (as well as any
similar problems that might have occurred in the future) by minimizing
the code paths that can be reached by rdata classes other than IN, so it
is safe for the implementation to assume that rdatatypes that are only
defined for class IN, such as SVCB or WKS, have been parsed and
validated, and not accepted as unknown/opaque data.

Fixes: isc-projects/bind9#5777
Fixes: isc-projects/bind9#5779
(cherry picked from commit a6d8e330ed6cf0021bff3f00aa1dc7a296f5aec0)