components-actual diagnostic skips content of component/unit errors

[faec]

The components-actual diagnostic reports the observed component state stored in (*Coordinator).State().Components. One part of this structure is Err fields on each component and unit. However, these are bare error objects, and the diagnostic relies on them to properly serialize themselves during YAML encoding, which many error types do not do. For example setting a component's error to Err: errors.New("extremely important error") will just be encoded to yaml as err: {}.

We should make changes to the internal error structures and/or the diagnostic's processing of Components to make sure we get the text content of these errors.

[elasticmachine]

Pinging @elastic/elastic-agent (Team:Elastic-Agent)