Add OfferedDeadlineMissed QoS event

[ivanpauno]

• Depends on Move org.ros2.rcljava.events.publisher_statuses to org.ros2.rcljava.publisher.statuses #12

[jacobperron]

I missed this for other statuses in previous PRs, but I think these member variables should be private and we can add getters for them. I think this will provide a bit better encapsulation (e.g. if symbol names change in the future, it's easier to deprecate a method than a member variable).

I don't think making them private has any impact on the native code setting their values.

[ivanpauno]

I think that passive data types only carrying data are a valid citizen in oop.
When the class doesn't have any invariant (relationship between fields) there's not much value on using private data, setters and getters.

if symbol names change in the future, it's easier to deprecate a method than a member variable

If we change the name of one of the members we're going to break all other clients, so I don't think that's going to happen.

---

I realized (late), that the generated java bindings for ROS messages doesn't expose the data and provides getters/setters instead.
Though I don't like that, maybe being consistent in event statuses is better.

If would prefer doing this change after merging all remaining PRs in the feature branch.

[ivanpauno]

Merged, we can solve this issue before merging the feature branch on master.

[jacobperron]

I'm ambivalent about it. Maybe we just leave it as-is and bring it up again when we open a PR upstream.

I'm not sure what the reasoning was to generating getters and setters for ROS messages; this too may be something we can change later upstream.

[ivanpauno]

Sounds good