[SPARK-3415] [PySpark] removes SerializingAdapter code

This code removes the SerializingAdapter code that was copied from PiCloud

Author: Ward Viaene <ward.viaene@bigdatapartnership.com>

Closes #2287 from wardviaene/feature/pythonsys and squashes the following commits:

5f0d426 [Ward Viaene] SPARK-3415: modified test class to do dump and load
5f5d559 [Ward Viaene] SPARK-3415: modified test class name and call cloudpickle.dumps instead using StringIO
afc4a9a [Ward Viaene] SPARK-3415: added newlines to pass lint
aaf10b7 [Ward Viaene] SPARK-3415: removed references to SerializingAdapter and rewrote test
65ffeff [Ward Viaene] removed duplicate test
a958866 [Ward Viaene] SPARK-3415: test script
e263bf5 [Ward Viaene] SPARK-3415: removes legacy SerializingAdapter code