Work on issue #74404949: Screen state usage API

Add usage stats tracking of screen time.  There are two new
events, one for when the device is an interactive state, the
other for when it is non-interactive.  Also add a whole new
usage stats API for retrieving aggregated data that is associated
with general events, not particular packages.  In this case
it allows you to find the time the device spent interactive
and non-interactive and the count of the transitions in to
each of those states.

Bug: 74404949
Test: atest CtsUsageStatsTestCases:UsageStatsTest\#testInteractiveEvents

Change-Id: Ibe6d55e2aecb0c8519b1358644378ec5c7a4250d