Refactor smoke tests to enable one-app-per-testcase runs

Also creates a special TestRunner which runs one app per testcase.  Note that
running the smoke tests with android.test.InstrumentationTestRunner will /also/
work, but will run all of the launchable activites in a single testcase called
testRunAllActivities.

Bug: 6128185
Change-Id: Iffedff7e6105bbca614778a4d294d3be421f19d6
3 files changed