Add new GN junit binary template and new GYP java binary template.

Add new GN junit binary template and new GYP java binary template.

Adds a new junit_binary template for gyp which makes it easy to
make new Junit test suites by setting a lot of the options and
necessary dependencies for you.

Also, adds a new java_binary.gypi file which uses the
create_java_binary_script.py similiar to how the java_binary
GN template works when main_class is specified. This lets
GYP and GN work similiar when building a junit binary, so
our test runner can run them the same way.

Finally, because of the slightly different way were now running
the junit binary, the java classpath contains all of the jars
instead of just the test jar (before we were running
java -jar test_jar.jar which set the classpath to just be
test_jar.jar). Therefore, we can simplify things and just look
in the classpath for the paths to the Robolectric dependencies
when running Robolectric junit tests.

BUG=

Review URL: https://codereview.chromium.org/1057783002

Cr-Commit-Position: refs/heads/master@{#324093}