[FEAT] Automatically use Ray Runner if Ray is initialized

[jaychia]

1. Automatically switches Daft to use the Ray Runner if a user calls ray.init(...) before running any Daft querying
2. Also switches behavior to try and deprecate the DAFT_RAY_ADDRESS environment variable so that we can centralize on the normal RAY_ADDRESS behavior

This PR ensures the following behavior:

• If a user explicitly calls daft.context.set_runner_ray/py, this overrides all behavior
  • If a user calls daft.context.set_runner_ray with a specified address, but Ray is already initialized, we warn them that their address is being ignored
• Otherwise, on first execution Daft will attempt to retrieve the runner config from the current environment:
  • Check for the DAFT_RUNNER environment variable for RAY/PY
  • Check to see if Ray is initialized, and if we aren't running in a Ray worker: RAY
  • Fallback onto: PY

Ray connection detection, on driver vs on worker:

Warning if set_runner_ray is called with an address after Ray is already initialized:

[codecov[bot]]

Codecov Report

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Additional details and impacted files

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