Update fill UI

1. Abstracted the fill/save view and window management
   in dedicated classs

2. Avoided the need of a second window to detect outside
   touches

3. Simplified the fill-ui window management

4. Moved the UI in its own package to ease mmigration to
   sys UI.

5. Removed hard-coded colors from the layout

6. Make sure the save UI cannot grow as wide as the screen
   as this would not look good on tablets

7. Update the save UI to look closer to mocks

Test: CTS tests pass
Bug: 35708258

Change-Id: Ia74a5aad6f16bba0047a9e8e61958c77af0d358d