Hide hotseat when bubble bar is expanded.

Added logic to stash the hotseat when on launcher home screen.

Bug: 280494203
Test: Manual:
http://recall/-/gx8ASgewUeUS3QYohfrd1J/fjfjUw296LRXUm9uYqXU4K
all tests in com.android.launcher3.taskbar
Flag: com.android.wm.shell.enable_bubble_bar

Change-Id: I67b298831eaed9c549a2fae7dc5a0d9fae51f7c4