This adds a function to the core surface to get process information
about the process(es) running in the terminal. Currently supported is
the PID of the foreground process and the name of the slave PTY.
If there is an error retrieving the information, or the platform does
not support retieving that information `null` is returned.
This will be useful in exposing the foreground PID and slave PTY name to
AppleScript or other APIs.
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