[Maintenance] Extract test setup/teardown helper for dom-using helpers

Original suggestion: https://github.com/emberjs/ember-test-helpers/pull/1113#discussion_r725155278

What to explore:
- if we can make all the dom-using tests use the same setup/teardown behaviors in a like `setupDomTest(hooks)` style helper.
In particular, this code is repeated everywhere:
```js
if (element) {
element.setAttribute('data-skip-steps', true);
element.parentNode.removeChild(element);
element = undefined;
}
```