Protobuf update

[kellrott]

Several updates to pipeline API and protobuf schema

• Updates GRIP to use the new protobuf library
• github.com/grpc-ecosystem/grpc-gateway/runtime -> github.com/grpc-ecosystem/grpc-gateway/v2/runtime
• Aggregations return stream of elements, rather then a single bucket or results
• In memory aggregation from #235
• Python library update from #233
• Github actions based continuous testing

[kellrott]

Merged into develop-0.7.0 branch