Dynamic Event Action Server

[mxgrey]

This implements the dynamic event action server proposed in this discussion.

This PR depends on another PR for rmf_internal_msgs.

To use the new feature in this PR:

• Create a composed task that contains a dynamic_event and dispatch it
• Implement a dynamic event action client that issues goals for the dynamic action event server to follow

@TanJunKiat Maybe your team can help with testing by contributing a simple Python script to rmf_demos_tasks that does the following:

• Subscribe to rmf/dynamic_event/begin to watch for a dynamic event to begin
• When a new dynamic event begins, make an action client for rmf/dynamic_event/command/<fleet>/<robot>, wait for it to connect, and then issue a command based on CLI arguments given by --category and --file similar to dispatch_json.py
• Wait for the event to finish and then quit

Let me know what you think and feel free to reach out for more guidance.

[TanJunKiat]

Thank you, @mxgrey, for taking the initiative to pilot this.

We will begin investigating this matter.

Would you prefer to create a dynamic_event branch in rmf_demos and for us to submit a pull request to that branch, or should we proceed directly to the main branch?

[mxgrey]

You can open a PR that directly targets main, and we'll merge all the related PRs at the same time.

If we find a reason later on for your changes to target a different branch, then I can edit your PR to retarget it when that's needed.