Change chrome_public_test_apk to be built using new build templates.

Change chrome_public_test_apk to be built using new build templates.

Changing chrome_public_test_apk to use the instrumentation_test_apk
template for GN and include build/android/test_runner.gypi for GYP.
For GN, this will ensure some test dependencies (such as the md5sum
binary used by the test runner) are being built. And for both GN and
GYP, it will create the file out_dir/bin/run_chrome_public_test_apk
which can be used to easily run these tests.

BUG=

Review URL: https://codereview.chromium.org/1154163016

Cr-Commit-Position: refs/heads/master@{#332978}