InputDispatcher_test: Verify all consumed events are traced

Introduce a test implementation of the tracing backend that tracks all
of the logged events. Whenever an event is consumed by an input channel
in any of the Dispatcher tests, we expect that event to have been
logged into the trace. If a consumed event is not present in the trace,
the test will fail.

Bug: 210460522
Test: atest inputflinger_tests
Change-Id: I3b19684c14334d9b2f455cee3b3cfad794a633c0