Improve Feature Coverage - Loadables

[luke-hill]

Create a new set of feature tests that validate loadable tests work and do wait for things to change.

Pitfalls to watch out for

• When adding these tests in, make sure the loadable has both positive and negative tests (for waiting for things too fast/slow)
• Ensure that we're not modifying the overall page behaviour (Might need new page)

[luke-hill]

ping @dgarwood. Think you mentioned you wanted to tackle some tickets.

This one or the other ones with Good for Newcomers are worth a shot if you're interested.

[dgarwood]

@luke-hill I'll see what I can tackle.

[luke-hill]

re-ping @dgarwood did you get anything for these?

[dgarwood]

@luke-hill I don't have anything I can push at the moment.

[luke-hill]

Closed by #363