REFACTOR: Move javascript tests inside discourse app

This is where they should be as far as ember is concerned. Note this is
a huge commit and we should be really careful everything continues to
work properly.

plugins/poll/test/javascripts/helpers/display-poll-builder-button.js.es6

@@ -1,4 +1,4 @@
-import selectKit from "helpers/select-kit-helper";
+import selectKit from "discourse/tests/helpers/select-kit-helper";
 
 export async function displayPollBuilderButton() {
   await visit("/");