Reticulate support improvements

[dfalbel]

A few working items for the next iteration of work in the Reticulate integration

• Option to stop initiating the reticulate environment as default Python interpreter until called by R #4870
• Restarting reticulate can lead to some undesirable UI side effects #4887
• Python (reticulate) variables pane not updating after changes from R #4869
• Reticulate: typing exit at the python console freezes the session #5022
• Force quitting reticulate python terminates Positron IDE #4982
• Shutting down the Reticulate Python kernel should restore the original sys.stdout and sys.stderr #5057
• Shutting down the Reticulate repl should return focus to R repl #5144
• Shutting down the R session should gracefully shutdown the Reticulate session #5083
• No passing R and Python object within reticulate session in Positron #5210
• Smoke test: reticulate #5419
• Support for reticulate in the Jupyter supervisor: Jupyter Supervisor known issues #4912
• Toggle the feature flag to default to TRUE

[t-kalinowski]

• Shutting down the Python kernel should restore the original sys.stdout and sys.stderr

[jmcphers]

The supervisor itself is going to need to take on some work to be able to support connecting to an existing session for Reticulate. I've filed that here: https://github.com/posit-dev/kallichore/issues/8