Update severe (5%/1 hour) warning to send through battery saver

Now that battery saver is sticky this notification never shows
and we are getting reports from people that the notification
they were expecting never showed up. It turns out that a lot
of these were due to people not realizing battery saver was on.
To remedy the worst case situation (your phone is about to die
soon but no 15%/3 hour notification came up) we should always
show the severe warning even if battery saver is on. This only
affects the hybrid warning, not the legacy percentage based
version.

Test: unit tests
Bug: 111596093
Change-Id: I92453b68b6ee8aad8f862147c877f4e789afc55c
Merged-In: I92453b68b6ee8aad8f862147c877f4e789afc55c