MiltiWaveView accessibility improvement.

Now hover events behave s motion events in touch exploration mode.
The use no longer needs to find the handle and tap + hold to engage.
It is enough to move on top of it.

Now the handle is engaged, i.e. can be dragged, when the user passes
on top of it for both accessibility enabled and disabled.

bug:5253968

Change-Id: If70b44cb6db8a38432216b46ecddefb3e2bc3825