feat(rust, python): add streamable udfs

[ritchie46]

Any function that can operate in batches can now be used in the streaming engine.

(pl.DataFrame({
    "a": [1, 2, 3]
}).lazy()
.map(
    f = lambda df: df.with_columns(pl.col("a").alias("b")),
    schema={"a": pl.Int64, "b": pl.Int64},
    streamable=True,
)).collect(streaming=True)

closes #6603