[SPARK-21985][PYSPARK] PairDeserializer is broken for double-zipped RDDs

## What changes were proposed in this pull request?
(edited)
Fixes a bug introduced in #16121

In PairDeserializer convert each batch of keys and values to lists (if they do not have `__len__` already) so that we can check that they are the same size. Normally they already are lists so this should not have a performance impact, but this is needed when repeated `zip`'s are done.

## How was this patch tested?

Additional unit test

Author: Andrew Ray <ray.andrew@gmail.com>

Closes #19226 from aray/SPARK-21985.