Add code coverage support for robolectric tests

- To run robolectric tests with code coverage, run:
    make RunSettingsRoboTests-jacoco -j44
- Generated reports are placed under
   $OUT/obj/FAKE/RunSettingsRoboTests_intermediates/coverage

bug:32617403
Test: Ran manually, verified that reports are generated.

Change-Id: Ie51ab86c5fbaa9297d717167fda04a555dadbfe8