Phoenix is no longer just a library, but is also a containerized application. We should update our logging accordingly.

• Add a setting that can be configured by an environment variable that will configure structured logs for Phoenix. By default, no non-standard logging configuration will be used so that Phoenix continues to act as usual when used as a library (e.g., in a notebook environment).
• Add a JSON formatter.
• Log off the main thread with QueueHandler.
• Use UTC timestamps.

Helpful introduction to Python logging: guide on modern Python logging.