[Python] Scan_parquet() should be able to accept directory as input

[lmocsi]

Description

As of polars version 0.20.7 pl.scan_parquet() only accepts reference to files.
Should be able to accept reference to a directory, like pl.scan_pyarrow_dataset() does.
Implementation seems quite simple: should just append '/**/*.parquet' to the given input directory, and you have the file reference, that can be fed to the existing pl.scan_parquet() function.

[Smotrov]

BTW /**/*.parquet would not work is parquet files have no extensions. Such files could be generated by AWS Athena for example.

For files with no extension /**/* would not work either, because it seams it is taking 0 byes folder objet into consideration and complaining that there is No Body

[nameexhaustion]

closed by #17017