Fixed a few bugs regarding big notification groups

The overscrolling was listening to the paddingOverflow
which didn't make sense. Also, we need to update the
top padding if the height of the first element changes.

This also fixes several cases where the notification size was
wrong when the quick settings panel was expanded.
It also fixes some flickering regarding the TopPaddingoverflow
which was going rogue in a few cases.
The transition from the locked shade is thereby also improved.

Change-Id: I703ea27879b325c02a15fdacee3b58f5ef78fd20
Fixes: 30801139