Add tests for ending TouchExplorer dragging

Increasing test coverage.

In the process, found a bug in dispatching up events for
multiple fingers. It was sending an action_up for each
pointer rather than a pointer up.

Bug: 148690104
Test: atest TouchExplorerTest
Change-Id: I04353bd4ad222d6bc4096a62de48b1fe00363b3a
2 files changed