Create mojo/edk/js, mojo/edk/js/test

Move mojo/bindings/js to mojo/edk/js.

Move mojo/bindings/js/tests/run_js_tests.cc into the test directory.

Move mojo/apps/js/test/handle_unittest.cc to mojo/edk/js

BUG=430520
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/690743003