Add better system(s) for testing content

[zoton2]

For the runs themselves it's easy to test with nodecg-speedcontrol, but other data is harder to test with right now, mainly data pulled/pushed from the donation tracker.

• Tracker API data (bids/prizes/donations)
• Pushed donations from tracker
• Pushed tweets
• Pushed subscriptions
• Pushed cheers
• Pushed crowd control messages
• Pushed "other stream" data (run information, game scene change)