Fixes to support transient taskbar in desktop mode

Track gesture progress in desktop visibility controller. We need to
allow launcher to resume when gesture is in progress and freeform tasks
are visible.
Update overview state handling in desktop visibility controller. When
overview is enabled, launcher should be made visible, regardless of
freeform state. When exiting overview state, check freeform state to see
what should be shown and enabled.

Bug: 263264985
Test: manual, enable transient taskbar, move app to desktop, invoke transient
taskbar
Test: manual, enable transient taskarb, enable desktop mode, invoke
transient taskbar
Test: manual, disable transient taskbar, move app to desktop, swipe up
to overview
Test: manual, disable transient taskbar, enable desktop mode, swipe up
to overview

Change-Id: I63000441d9cf72769e6efb9d247ab4112c01839d