Add basic UI test for apps

Given https://github.com/android/health-samples/issues/209, we should have a minimal test that launches the app at least, but ideally starts and stops exercise or tracking.

cc @ithinkihaveacat

Start by reading issue 209 and inspecting the apps in this repository to identify the appropriate UI-test entry point. Define the minimal expected flow from the issue: launch the app, with starting and stopping exercise or tracking as the optional broader goal. Done means an automated test covers at least successful app launch.

Written by the indexing model from the issue text.