Proto messaging support

[tudorcebere]

Pull Request

Description

Adding protobuf support for messaging, currenly, WorkerCommandMessage is not supported due to the fact that the test format only works for msgpack, not for protobuf as well. Will open an issue to rewrite that test.

Affected Dependencies

List any dependencies that are required for this change.

Type of Change

Please mark options that are relevant.

• Bug fix (non-breaking change which fixes an issue)
• Documentation (non-breaking change which adds documentation)
• Improvement (non-breaking change that improves the performance or reliability of existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How has this been tested?

• Describe the tests that you ran to verify your changes.
• Provide instructions so we can reproduce.
• List any relevant details for your test configuration.

Checklist

• I did follow the Contribution Guidelines
• I did follow the Code of Conduct
• I have commented my code following the OpenMined Styleguide
• I have added tests for my changes

Additional Context

Please also include relevant motivation and context.

[codecov]

Codecov Report

Merging #3638 into master will decrease coverage by 0.01%.
The diff coverage is 91.86%.

@@            Coverage Diff             @@
##           master    #3638      +/-   ##
==========================================
- Coverage   94.76%   94.74%   -0.02%     
==========================================
  Files         182      182              
  Lines       17949    18032      +83     
==========================================
+ Hits        17009    17085      +76     
- Misses        940      947       +7     

Impacted Files	Coverage Δ
syft/messaging/message.py	92.88% <91.25%> (-0.87%)	⬇️
test/serde/protobuf/test_protobuf_serde_full.py	100.00% <100.00%> (ø)