new: doc: Prepare documentation for BIND 9.20.2

The statements that already exist in the grammar can't be created with
the namedconf:statement. Use a plain definition list for these
statements and add a manual anchor for each one so links to them can be
created.

Avoid using the :any: syntax in the definition lists, as that just
creates a link to the duplicate and completely unrelated statement,
which just makes the documentation more confusing.

Merge branch 'nicki/prepare-documentation-for-bind-9.20.2' into 'v9.20.2-release'

See merge request isc-private/bind9!738