Running uROS on the MCU without the Agent running on a PC

Hey @pablogs9!
@CLansdaleBEC and I were talking about what it looks like for the MCU to run its respective nodes without the Agent running.

I could not quite recall if you had previously mentioned that it was a known limitation the MCU needed to communicate to the agent and then back down.

For instance:
Node A on MCU publishes message "Hello" -> Agent on PC -> Node B on MCU subscribes to topic and receives message "Hello"

Rather than
Node A publishes message -> Node B subscribes to topic and receives message.

I hope my question makes sense, but for our use case we are utilising the MCU as a safety critical system (meaning it handles some logic to ensure that in the fail case of it being unable to communicate with our PC, we publish commands to the rest of the MCU nodes so they can handle their respective parts).

The issue names no files, tests, or entry points. Start by reading the 24-comment discussion and the micro-ROS Agent architecture to determine whether MCU-to-MCU communication without an Agent is supported or requires a new design. Done should be a documented decision with a defined implementation scope, if work is needed.

Written by the indexing model from the issue text.