Dynamic density change handling

- In PWM, make sure to read the height values after the new
configuration has been applied.
- Reset all navigation bar button icons when density changes.
- Adjust height of notification bar.
- Reload divider height values in SysUI and WM.
- Snap divider handle to a new position after loading the
new configuration, as the snap points change.

Bug: 26844819
Bug: 27450471
Bug: 27921696
Change-Id: I9e28f0c49f6367c5fcfac010e7a6e98a42e85996