Deprecation: Native dom helpers should not be used as globals in tests anymore

# Problem

Using native dom helpers as globals is now deprecated in our tests. Instead, we should add a new dependency to our app and import these helpers from it in any tests that need it.

We are leaning away from these anyway, due to relying on ember-cli-page-object, but there are still a couple of places where we do use them.

## Subtasks
- [ ] Install depdencency https://github.com/cibernox/ember-native-dom-helpers
- [ ] Search through our tests for usage of the `find`, `click`, `fillIn`, `visit` and other global functions in this group. Careful not to mistake them for the identically named functions provided by `ember-cli-page-object`. The culprits we need to fixed are likely used as globals, in tests, directly.
- [ ] In any module that uses them, import them using `import { visit, click, find, fillIn } from 'ember-native-dom-helpers';`