Use accessibility action for touch exploration

Explore-By-Touch has been dispatching touch events to the screen
rather than using the accessibility API. This was intended as a
workaround for apps that did not properly handle accessibility,
but the workaround itself has been causing bugs in corner cases
where properly accessible Views are partially covered by windows.

This CL first tries to dispatch a click action, and falls back on
the touch dispatch only if the click action fails.

Bug: 35200501
Bug: 26216304
Bug: 20665958
Bug: 34949365
Bug: 34844480
Bug: 29535082

Test: Poking around with first party apps and TalkBack works fine.
This behavior isn't covered by automated testing.

Change-Id: I9cc18399d8f40f7381dfcbef91b5991b711bb7f1