Don't create custom elements in main and fix various small issues on tests (#747)

* Create custom elements when the runtime finishes loading

* Remove xfails and fix repl integration test

* Fix commented ignore

* Address Antonio's comments

* Fix bad rebase

* Make ure to wait for repl to be in attached state before asserting content

* Move createCustomeElement up so it runs before we close the loader, xfail flaky d3 test

* Fix xfail

pyscriptjs/tests/integration/support.py

@@ -191,6 +191,9 @@ class PyScriptTest:
             timeout=timeout,
             check_errors=check_errors,
         )
+        # We still don't know why this wait is necessary, but without it
+        # events aren't being triggered in the tests.
+        self.page.wait_for_timeout(100)
 
     def pyscript_run(self, snippet, *, extra_head=""):
         """