feat: serialize/deserialize LazyFrame

[eitsupi]

The Python class method polars.LazyFrame.deserialize() cannot be expressed well here, so I assigned a function pl$deserialize_lf().
The function name could be change.

In addition, in Python, these functions can also have files as input/output destinations, but here I am simplifying to interacting with character vectors. Reading and writing to files must be done by other functions.

[eitsupi]

It might be worthwhile to enable the format to be specified as chracter or raw, as in nodejs.
https://pola-rs.github.io/nodejs-polars/interfaces/pl.LazyDataFrame.html#serialize

[etiennebacher]

Thanks, I don't know much about serializing/deserializing but LGTM. Should we add a comment about security concerns when deserializing an unknown input as they do in the py-polars docs?

[eitsupi]

Should we add a comment about security concerns when deserializing an unknown input as they do in the py-polars docs?

I think there is a special feature for Python that saves Python objects as pickle for Python.
I don't think the concern exists because there is no R-only functionality here and Polars does not restore anything like rds files.