Add gRPC streaming for code first approach

[vasylstrogushr]

There is no approach using gRPC streaming in .Net Code First approach.
One of the solution is to use IAsyncEnumerable but it is not for a streaming but mostly about duplex connection.

P.S. If using protobuff first approach it works fine but in .Net ecosystem I would like rather use code first approach with Code First Grpc Reflection to provide contracts to other services that sending protofiles.