Temporarily whitelist processes to open activities from background

when service-based PendingIntent was whitelisted

Extends the mechanism added for broadcasts in ag/5779089.
The process can start activity from background when whitelisted
PendingIntent-based Service was started - for the next 10 seconds,
or until the service is stopped, whichever happens sooner.

For now, all this is only wired for notifications.

Bug: 110956953
Test: atest WmTests:ActivityStarterTests
Test: manual with Calendar notifications that are known
      for doing Service trampolines
Change-Id: If6ed2f5e22403c4df5abb6cf876ae89505e57380