This change lets the test runner accept the same isolated script
parameter syntax as Chromium. It keeps the old parameter names so
the tests accept both. This will let us more easily integrate with
the Chromium Android test_runner.py script.

Also update the README which was missing a few flags.

Bug: angleproject:3162
Change-Id: Ic22b289a095418ffdaa19a04caa1b45c6c657872
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2300530Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>