Update the bubble bar offset on Home

This is an initial change that positions the bubble bar aligning it
with the center of the hotseat icons. We still need to center it
with the taskbar when in overview.

This change also fixes the touch issues where sometimes the hotseat
icons don't respond to taps. The fix is twofold:

1. Make sure that taskbar insets are always updated when
   BubbleStashController#setBubblesShowingOnHome is called.
2. Update the touchable region in TaskbarInsetsController to account
   for the Y translation of the bubble bar bounds when the bubble
   bar is visible.

Demo: https://screenshot.googleplex.com/6NRyu2CR7Bjs32x

Bug: 286247080
Test: Manual on a physical device
Change-Id: I00daff8341e4d8f5d141b5e0220726f6c03b437c