Coalesce the shared GID battery usage into its real UID

Also skip isolated UIDs as they've been attributed to their parent
processes' battery usage.

Bug: 203105544
Test: atest FrameworksMockingServicesTests:BackgroundRestrictionTest
Test: manual - adb shell dumpsys activity -a
Change-Id: I16a5537efe7fa8728c5fc7dca79bcc6fc717a161