Remove layoutTransitions for current FAB and use custom animation.

Have background contain left and right padding of 16dp.
That way upon collapse, its easier to animate so that every other view's space but the icon is removed.
Spec when expanded/collapsed: https://www.figma.com/design/uMzPkNMZpb7EyfHDo8usIa/V-%E2%80%A2-Toast-Butter?node-id=2839-365095&node-type=text&m=dev

bug: 361589193
Test: manually - video:https://drive.google.com/file/d/1K7HCpayZBa_oo9p3XV10QQX4miTy_d3q/view?usp=sharing
withRTL: https://drive.google.com/file/d/1NfUEyEvzjfQamujv4EqLNBqB47mPNG1Y/view?usp=sharing
Flag: NONE just changing expandedFAB to use custom animations from layoutTransition

Change-Id: I7948633850a1010175eb4f0248daff22cf2f2c87