Fix BottomNavigationMenu item selection via Menu object

- Move the logic of handling which item is checked to MenuBuilder instead of
  BottomNavigationMenu itself by making all the MenuItems exclusively checked.
- Fixes MenuBuilder#startDispatchingItemsChanged to call onItemsChanged
  with a correct value of structureChanged. It now keeps track if structure
  changes while dispatching is prevented.
- Added a button to focus the next bottom navigation item to
  BottomNavigationViewUsage

Bug: 32336752
Test: Added a new test to BottomNavigationViewTest

Change-Id: Ief3ff356b501373aaabdd5f4990ecf6f9c506f05
8 files changed