Add FLAG_ONLY_ALERT_ONCE to direct reply update

Adds FLAG_ONLY_ALERT_ONCE to the update we sent from system_server to
systemUI on direct reply, to transition the notification out of the
sending state and to the sent state.

This update should only be used to update the appearance of the
notification; it should not alert, because it's triggered by the user's
direct reply action, and the user already knows they direct replied
(they're the ones who did it). We already setPostSilently on the
notification record, but that just prevents beeping, buzzing, and
blinking; it doesn't prevent the notification from HUN-ing if, for
example, the enqueued update somehow gets re-triggered by the app (see
attached bug).

Modified unit tests to check we're adding this flag.

Bug: 335106917
Test: atest NotificationManagerServiceTest
Flag: ACONFIG android.app.lifetime_extension_refactor STAGING
Change-Id: I521d83eea27e7026e1050a27856ef86013fd659f