Adjusting touch explorer to fix split tap behavior discrepancies

Avoids sending TOUCH_INTERACTION_END on double tap if there is still at least one pointer down.
This avoids a duplicate event being sent when the last pointer leaves the screen.

Updates tests to account for this change as needed.

Flag: com.android.server.accessibility.pointer_up_motion_event_in_touch_exploration
Bug: 374930391
Test: atest TouchExplorerTest (both FW and CTS)
Change-Id: I0c7a0dcfdcd595840c79291aac9b290740cae468