API: to/from polars #978
Description
It would be pleasant to support to/from operations for both pl.DataFrame and pl.LazyFrame.
Mirroring duckdb, it would be pleasant to alias to_polars_dataframe as .pl().
In addressing this issue, the to_dataframe method should be renamed to to_pandas_dataframe, with to_dataframe aliasing against it to preserve the API. We should additionally provide a short hand of .df() for obtaining the frame.