migration: Drop migration_is_setup_or_active()

migration: Drop migration_is_setup_or_active()

This helper is mostly the same as migration_is_running(), except that one
has COLO reported as true, the other has CANCELLING reported as true.

Per my past years experience on the state changes, none of them should
matter.

To make it slightly safer, report both COLO || CANCELLING to be true in
migration_is_running(), then drop the other one.  We kept the 1st only
because the name is simpler, and clear enough.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>