Test non default pickle library

The python SDK recently added support for the cloudpickle library though the default is still dill. See [_https://s.apache.org/beam-picklers_] and https://issues.apache.org/jira/browse/BEAM-8123.

We intend to switch this over to cloudpickle as the default.

We should have a suite of E2E tests to make sure we don't introduce regressions into whichever pickle library is not the default.  That is to say:

First -  E2E tests for the using the cloudpickle library.

After cloudpickle library becomes the default - switch these E2E tests to cover dill.

This will allow test coverage while we hopefully transition to just supporting a single library.