[BadgeDrawable] Allow to set drawable as a background

**Is your feature request related to a problem? Please describe.**
There is no chance to add stroke to badge which is great to have in case BottomNavigationView.Item's icon color is the same as badge's color

**Describe the solution you'd like**
Allow to customize background with drawable

**Describe alternatives you've considered**
- Allow to customize strokeWidth and strokeColor of internal ShapeDrawable

**Additional context**
I wouldn't mind to contribute with PR if there will be final decision on solution/approach

- Allow drawable background
- Allow to customize strokeWidth/strokeColor

Start by reviewing BadgeDrawable and the issue discussion to determine whether customizable drawable backgrounds or strokeWidth/strokeColor is the accepted approach. Trace the existing background behavior and identify the relevant Android UI tests; done means the chosen customization is supported and its behavior is covered by tests.

Written by the indexing model from the issue text.