Update taskbar window size for flyout

This change updates the taskbar window size after the flyout view
has measured itself. This ensure that the taskbar window is tall
enough to display the entire flyout.

When the flyout is removed we reset the taskbar window size.

Flag: com.android.wm.shell.enable_bubble_bar
Bug: 277815200
Test: builds successfully and tested manually -- code is not wired up
Change-Id: I5e8618e57443212e1c4f19ab20d1542ae2d1b865