[rust]: Consume arrow record batches in Polars DataFrame

[prrao87]

In Python, we are able to use the get_as_arrow() and get_as_pl() methods to consume a QueryResult and transform it to an Arrow table or Polars DataFrame. Because we can already produce an arrow iterator over the query results in the Rust API now, I'm wondering if we can allow a get_as_pl() method in Rust to obtain the results in Rust Polars as well?

@benjaminwinger what do you think? DataFrames are a great way to work with tabular data and it would be nice to support Polars in Rust as well as Python.