Add new metrics to report averages as sum and count

This CL will introduce new metrics for reporting separately the sum
(numerator) and count (denominator) of the average metrics currently
defined, as average values (or any non-monotonic metric) currently
cannot be aggregated gracefully as Value Metrics in StatsD.

Test: atest art_standalone_libartbase_tests
Test: atest art_standalone_runtime_tests
Test: ART run-test 2232-write-metrics-to-log

Bug: 229618060
Bug: 240165346

Merged-In: I88741e38b5e9fa784efa57cc9ef079dd7ee4c447
Change-Id: Ib19be794fcda579f74703cc0d1db9df5197588f3
5 files changed