Fallback to ML prediction after short ACTIVE states

When an app is temporarily elevated to ACTIVE state for some
reason, keep track of the last predicted bucket and drop back
to that if the ACTIVE state ends.

Also keep track of prediction during a forced ACTIVE state, even
if it's not applied right away.

Bug: 77158823
Test: atest AppStandbyControllerTests
Change-Id: Ic6de6c24bb25c5392ac5b41a2c05889d94f23436