## What changes were proposed in this pull request?
In this PR we've done two things:
1) updated the Spark's copy of cloudpickle to 0.6.1 (current stable)
The main reason Spark stayed with cloudpickle 0.4.x was that the default pickle protocol was changed in later versions.
2) started using pickle.HIGHEST_PROTOCOL for both Python 2 and Python 3 for serializers and broadcast
[Pyrolite](https://github.com/irmen/Pyrolite) has such Pickle protocol version support: reading: 0,1,2,3,4; writing: 2.
## How was this patch tested?
Jenkins tests.
Authors: Sloane Simmons, Boris Shminke
This contribution is original work of Sloane Simmons and Boris Shminke and they licensed it to the project under the project's open source license.
Closes#20691 from inpefess/pickle_protocol_4.
Lead-authored-by: Boris Shminke <boris@shminke.me>
Co-authored-by: singularperturbation <sloanes.k@gmail.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
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