Build MojoRunnerApptests.apk for mojo_apptests target on Android.

The FYI 'Chromium Mojo Android' bot is failing the apptests step:
https://build.chromium.org/p/chromium.mojo/builders/Chromium%20Mojo%20Android
..."MojoRunnerApptests.apk is neither a directory nor file"...

Also add other apptest targets from mojo:tests.

BUG=NONE
TEST=FYI bot gets closer to passing apptests step.
R=sky@chromium.org
TBR=ben@chromium.org

Review URL: https://codereview.chromium.org/1683063003

Cr-Commit-Position: refs/heads/master@{#374821}