Remove LatencyStatistics from dispatcher

Currently, InputDispatcher is sending touch event information to
westworld. We will now be transitioning to new atoms that have better
coverage and statistical significance.

In this intermediate CL, we remove the LatencyStatistics so that we can
replace it with something better in the upcoming CLs.

Bug: 167947340
Test: m libinput_tests inputflinger_tests
Change-Id: I8fcb846321245011c3b6e6f896b99b8d9037a2a4