Make the test-wpt mach command support all the command line arguments of wptrunner.

Also remove the shell script and ensure that default options are set in a single location

tests/wpt/run_wpt.py

@@ -0,0 +1,19 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#!/usr/bin/env python
+
+import run
+
+paths = {"include_manifest": run.wpt_path("include.ini"),
+         "config": run.wpt_path("config.ini")}
+
+def run_tests(**kwargs):
+    return run.run_tests(paths=paths, **kwargs)
+
+def main():
+    return run.main(paths)
+
+if __name__ == "__main__":
+    sys.exit(0 if main() else 1)