Handle reset for ultimate-trial-paid-customer plan

GitlabSubscription before_update callback `reset_seat_statistics` needs
to handle ultimate-trial-paid-customer plan differently. During the
ultimate-trial-paid-customer period, we want to continue the premium
plan's seat statistics and QSR, as if the namespace is still under the
premium plan. Thus we should not reset_seat_statistics when starts(and
expires) ultimate-trial-paid-customer plan. There are several scenarios:
- premium=>ultimate-trial-paid-customer, do not reset_seat_statistics
- ultimate-trial-paid-customer=>premium(not renewed), do not
  reset_seat_statistics,
- ultimate-trial-paid-customer=>premium(renewed), reset_seat_statistics
- ultimate-trial-paid-customer=>ultimate, reset_seat_statistics

Changelog: changed
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/137243
EE: true