[Feature Request] Allow Opening Ports on Elastic Agent Container

[MakoWish]

As it is now, the Elasticsearch container opens port 127.0.0.1:9200, the Kibana container opens port 127.0.0.1:5601, and the Fleet Agent container opens port 127.0.0.1:8220. Unfortunately, the Elastic Agent container does not open any ports at all, and there does not appear to be a way to open one.

It would be nice to have a feature that allows opening custom ports, preferably allowing an externally accessible port like 0.0.0.0:9010, so package development can be done with live data. This would exactly match a production environment, from source, to final indexed documents, instead of relying on a fixed set of sample logs using Stream. This would give the best chance of catching anomalous events during development, as well as a complete A-to-B test of the integration.

[jsoriano]

Related: #1262