Handle mismatched task root on Activity resume and stop

It is possible for UsageStats to recieve activity resume and stop events
for the same activity, that have different task roots. Change UsageStats
to report usage start/stop to AppTimeLimitController using only the
package name on Activity pause.

Fixes: 169970833
Test: atest android.app.usage.cts.UsageStatsTest
Change-Id: Ie0ff4a18bf2001f72f637cc1687b7bd0a5afa85e