Fix system tests for when billing is enabled

[gazayas]

Closes #782.

Since our billing page has changed, we needed to update the test helper that fills out the necessary fields to subscribe to a plan.

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There are still a bunch of system tests that need to be updated, so I'll mark the PR as ready for review once those are done.

[gazayas]

Because the pricing page can take a while to finish and then redirect, I had to add some extra sleep calls to make sure everything passed. The tests now unfortunately take a while when billing is enabled, but I don't think we can do much about it if request to subscribe to the plan takes a long time.

If anything I can double check on the numbers and try to cut them down if necessary.

[gazayas]

Actually, now that I'm thinking about it we might have to remove free_trial? and use freemium_enabled? exclusively. I think I'll run tests again with the latter and push that if it aligns with how we want to handle free subscriptions.

[gazayas]

Ok, I made the sleep times shorter, and since we don't go to the pricing page when a freemium is enabled, I removed the unnecessary checks from the application system case because we skip this inside each system test anyways.

[jagthedrummer]

@gazayas This looks great! Can you resolve the conflicts?

[gazayas]

@jagthedrummer Done!