Move mojo/apps/js tests et al to mojo/edk/js/test,tests

The apps_js_unitttests test executable is now called js_integration_tests.

The connection_unittests are now included in the JS unittests. To enable that the threading module, which just provides a quit method, was added to mojo/public/js. Its implementation is mojo/edk/js.

Integration tests are in the edk/js/tests directory and test support code is in edk/js/test.

BUG=430520
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/709603002
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index 6595b13..6851110 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -64,10 +64,10 @@
   testonly = true
   deps = [
     "//mojo/application_manager:mojo_application_manager_unittests",
-    "//mojo/apps/js/test:apps_js_unittests",
     "//mojo/common:mojo_common_unittests",
     "//mojo/converters/surfaces/tests:mojo_surfaces_lib_unittests",
-    "//mojo/edk/js/tests:js_unittests",
+    "//mojo/edk/js/test:js_unittests",
+    "//mojo/edk/js/test:js_integration_tests",
     "//mojo/edk/system:mojo_message_pipe_perftests",
     "//mojo/edk/system:mojo_system_unittests",
     "//mojo/public/c/system/tests:perftests",