More coroutines cleanup

[hopskipnfall]

Primary changes:

• Uses a buffered Channel instead of a BlockingQueue which should improve resource usage for coroutines a lot
• Don't launch request handlers asynchronously. This would be nice but I don't think it's necessary or particularly helpful for us.
• Better logging and cleanup logic. Hopefully this gets rid of some orphaned coroutines.
• Remove some unused code.
• Sets the number of Dispatchers.IO coroutine handlers to 1K.