The dns_test_makezone() helper function always assigns the created zone
to some view, which is not always necessary and complicates cleanup of
non-managed zones as they are required not to be assigned to any view.
Rework dns_test_makezone() in order to make it easier to use in unit
tests operating on non-managed zones. Use dns_name_fromstring() instead
of dns_name_fromtext() to simplify code. Do not use the CHECK() macro
and add comments to make code flow simpler to follow. Use
dns_test_makeview() instead of dns_view_create().
Adjust existing unit tests using this function so that they still pass.
(cherry picked from commit bfbeef3609)
(cherry picked from commit f70c02d2c2)
(cherry picked from commit d45ee39bae)
(cherry picked from commit d76fdb8718)
c7d9100dcb