Add agent-driven monitoring integration tests

We currently have tests to verify that stack monitoring works for internal collection, and metricbeat collection, but we do not have any testing to verify that agent driven monitoring can collect data, and populate indices to enable dashboards to work.

We should add integration tests to verify.

Start by locating the existing integration tests for stack monitoring with internal collection and Metricbeat collection. Add equivalent coverage for agent-driven monitoring, verifying that data is collected and the expected indices are populated so dashboards can work; the integration test suite should pass.

Written by the indexing model from the issue text.