Update standby buckets for restored apps.

When apps are restored, set their standby bucket to RARE if
they have been used within the past 90 days, based on the
restored UsageStats data.

Bug: 214580000
Test: atest UsageStatsDatabaseTest
Change-Id: I9d63032ef84fef97734b51323f41b797caa4f554
(cherry picked from commit 89f69113)