Increase timeouts in FakeInputDispatcherPolicy

We are speculating that these timeouts are too short, and therefore the
tests are flaking occasionally.

At the same time, do some more cleanups:
- remove the flag that's already rolled out
- increase the speed of user activity poke tests

Bug: 424941803
Test: atest inputflinger_tests
Flag: TEST_ONLY
Change-Id: Ic2c9180d09b3bf02aa8cd4dbe89e1d38c33b885a