update Messages and Communication documentation do show how to define messages in .proto

[rysweet]

What feature would you like to be added?

need to update this page: https://microsoft.github.io/autogen/dev/user-guide/core-user-guide/framework/message-and-communication.html to show also how to define messages in .proto

Why is this needed?

its convenient and also needed for xlang

[ekzhu]

For the start document the GrpcWorkerRuntime to note the proto message types are required for x-lang.

Also the distributed runtime framework section as well