In NotificationRecord, clean out adjustments once they've been applied.

This frees up some memory and prevents unnecessary re-processing of
the adjustments.  It also deduplicates the NOTIFICATION_ASSISTANT tron
log record that is written every time a new notification is
created. It also prevents any other duplication of event logs.

Bug: 122823423
Test: atest SystemUITests NotificationAssistantServiceTest  and manual testing.
Change-Id: Ie2514e8e9ac19f79b1ad0afcde4d96649fe28069