Light refactoring of catz.c

Light refactoring of catz.c

* Change 'dns_catz_new_zones()' function's prototype (the order of the
  arguments) to synchronize it with the similar function in rpz.c.
* Rename 'refs' to 'references' in preparation of ISC_REFCOUNT_*
  macros usage for reference tracking.
* Unify dns_catz_zone_t naming to catz, and dns_catz_zones_t naming to
  catzs, following the logic of similar changes in rpz.c.
* Use C compound literals for structure initialization.
* Synchronize the "new zone version came too soon" log message with the
  one in rpz.c.
* Use more of 'sizeof(*ptr)' style instead of the 'sizeof(type_t)' style
  expressions when allocating or freeing memory for 'ptr'.