Plugin expressions don't handle keyboard interrupts (CTRL+C)

[sclamons]

Long-running plugin expressions can hog the terminal and can't be interrupted by keyboard interrupt. This is a known phenomenon with PyO3: https://pyo3.rs/v0.23.3/faq.html. Recommended practice is for long-running functions to occasionally call Python::check_signals(), which lets the Python interpreter check for SIGINT and other signals; but I can't find a way to do that from a Polars plugin, where you don't typically have access to a Python object.

It would be really nice for PyO3-polars to handle SIGINT checking behind the scenes. Barring that, can we somehow allow access to the Python object that ultimately gets used in the call? If there's already a way to do this, it needs to be documented (or documented better).