Add an application test runner for mojob.py support.

Add a python apptest runner with fixture isolation.
(this avoids persistent state in service dependencies)
Run apptests via mojob.py (for now, test harness later).

Add a python helper to parse --gtest_list_tests output.
Add a unit test for the gtest_list_tests() helper.
Run mojo/tools/mopy tests via run_mojo_python_tests.py

TODO: Fail on errors! mojo_shell always exits with 0!
TODO: Cache results? Need transitive hash of binary...
TODO: Run some apptests without fixture isolation?
TODO: Add shell/test/runner arg support, etc. (harness)

BUG=392646
TEST="$ mojo/tools/mojob.py test" runs our current apptests. apptest_runner.py also works directly.
R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/660093005