Starting Unit Tests for Metrics

After searching around, I discovered that our cts unittest location is
unable to find the correct dependencies for the build (even though
aidegen was able to). I discovered, instead, that we need to land our
unittests in the services/tests directory, since the MetricUtilities are
found in the services/.../server package.

I've left TODOs where necessary.

Bug: 273339472
Test: These are Metric Unit Tests
Change-Id: Idf84ec5fc05ced6ca39c4b9bde557a04542823b1