Add e2e test for Beats monitoring

[axw]

There exist system tests for libbeat/monitoring, using mockbeat, which have been skipped due to flakiness: #16247. These tests do not cover running inside Docker, a common deployment method.

We should introduce new end-to-end monitoring tests which run Beats, including as Docker containers. By including Docker containers in the tests, this will help ensure problems such as #22844 do not reoccur.

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[botelastic]

Hi!
We just realized that we haven't looked into this issue in a while. We're sorry!

We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1.
Thank you for your contribution!