Track basic TARE statistics.

Track some basic statistics to see how TARE performs over time. They'll
only be kept and viewable locally. We can continue to refine them to
determine what's useful and necessary.

Bug: 158300259
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/tare
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/tare
Change-Id: Ia408b9fc2b688a850fe8974ac473613711711a15