Don't allow scrolling RecentsView outside navbar during quickswitch

Once the inputProxy (OverviewInputConsumer) was enabled, it was never
disabled. And while it was enabled, touches above the nav bar would go
through to launcher, allowing you to scroll RecentsView (for example)
during quick switch transitions. This breaks some assumptions, since
it doesn't go through our normal shared swipe state logic that cancels
the animation, updates the new end target (e.g. NEW_TASK vs LAST_TASK),
etc. Thus, if you tried returning to LAST_TASK via this route, we would
end up starting it as a new activity instead of resuming the existing
one, causing a flicker (I guess because that TaskView is hidden).

Test:
- Swipe up from task A to home (to enable input proxy)
- Open A
- Swipe to B, and during transition scroll back to A from the center of
the screen

Before, this caused a flicker, now the last scroll is ignored.

TODO: we should increase the nav region during quick switch to make it
easier to continue scrolling

Bug: 136829198
Bug: 138620399
Change-Id: I5ffb53743b728e1909066c5dd18cc9308aff2c7e