Update sizes for the bubble avatar

* Update sizes of badge & bubble; also simplify some of the sizing
  code, we can do it with just the overall size
* Simplified things, instead of the inner / outer sizes just use
  the overall size

Test: visual - create a bubble and look at the size of the bubble and
               badge
      visual - have some bubbles, change display size, create a new
               bubble & verify that all of the sizes are the same
Bug: 183657577
Change-Id: Ibd8609a8737bb0a57519fa70fba17138bb69b379