Refactoring DigitalWellbeing Banner to not use footers.

Removing use of footers as they are no longer necessary. Refactoring DWB code to a separate class to be cleaner. Also fixes bug with DWB animating in twice.

Bug: 171317883
Bug: 171317874
Tested:Manual

Change-Id: I78c4e541e7afa76301c3afc373ab3fa251a2c3b0