Add component/unit information to elastic_agent.status_change dataset

**Describe the enhancement:**
Have the component/unit information fields on the elastic_agent.status_change dataset logs, like we have on the elastic_agent dataset. This would allow to know the component/unit that caused the status change on the host.

**Describe a specific use case for the enhancement or feature:**
If I want to get an alert when a host became Unhealthy only if its Elastic Defend integration failed.

**What is the definition of done?**
Having the following field on elastic_agent.status_change dataset logs:
- component.id
- component.state
- unit.id
- unit.state

OR

Having the field on elastic_agent.status_change dataset logs:
- reason for status change