rework queue system

[machineonamission]

currently the "queue" is an asyncio semaphore. this works, but really i should implement something custom

it should have the following properties:

• similar functionality (FIFO queue where a specific number of tasks can execute at once)
• queue priority (bot owner gets top priority, leaves room in the future for mediaforge subscription to prioritize over free users)
• queue position can be known, perhaps instead of just blocking, it returns an object that updates or something

some stretch goals

• not really queue itself, but if the bot crashes, the queue commands get deleted