[elastic-agent] Improve status output for different applications

[ruflin]

Elastic Agent runs a second instance of filebeat and metricbeat for monitoring. When running elastic-agent status the output looks as following:

Status: HEALTHY
Message: (no message)
Applications:
  * filebeat	(HEALTHY)
    Running
  * metricbeat	(HEALTHY)
    Running
  * filebeat	(HEALTHY)
    Running
  * metricbeat	(HEALTHY)
    Running

There is currently no way to differentiate between the different processes which are running. If one of the filebeat instances would be unhealthy it is not possible to see which one. Internally the processes have different names / id, would be good to show this here.

[elasticmachine]

Pinging @elastic/agent (Team:Agent)