InputDispatcher_test: Consume all moves to prevent events from batching

InputDispatcherTest uses a real input channel, which means if subsequent
MOVE events are not consumed, they will be batched together.

Currently this applies to windows with split touches, where pointers
moving on one split window will generate MOVEs on the other window which
the test is not consuming, and thus end up getting batched. Avoid this
situation by explicitly consuming all MOVE events in affected tests.

Bug: 210460522
Test: atest inputflinger_tests
Change-Id: I308c12e2aaf98f630bdac8021f7238e913a49056