Enhance compatibility with protobuf >=4.0

[wp19991]

• I have made modifications to the import statement in fed/proxy/barries.py to point to the correct file based on the version.
• The unit tests can now be passed using pytest -s -v tests/test_fed_get.py.
• The files fed_pb2_via_protobuf4.py and fed_pb2_grpc_via_protobuf4.py are generated under the protobuf4 version.
• The specific versions of protobuf4 and grpcio-tools are protobuf==4.23.4, grpcio==1.56.0, grpcio-tools==1.56.0.
• To execute the command, please run cd fed/grpc && python -m grpc_tools.protoc -I ./ --python_out=./ --grpc_python_out=./ ./fed.proto. I have also modified the names of the generated files from fed_pb2.py and fed_pb2_grpc.py to fed_pb2_via_protobuf4.py and fed_pb2_grpc_via_protobuf4.py.

Close #102

[fengsp]

@wp19991 Which ray version support protobuf >= 4.0? Does ray support protobuf 4.X and 3.X both too?

[jovany-wang]

This is awesome! Thanks for the contribution!