[Elastic Agent] Should report count of all agents, including the one sending only monitoring data

### Integration Name

Elastic Agent [elastic_agent]

### Dataset Name

_No response_

### Integration Version

2.6.7

### Agent Version

9.2.2

### Agent Output Type

elasticsearch

### Elasticsearch Version

9.2.2

### OS Version and Architecture

NA

### Software/API Version

_No response_

### Error Message

_No response_

### Event Original

_No response_

### What did you do?

Configured an Elastic-Agent to send the monitoring data to the monitoring cluster and the integration data to the main cluster.

Opened the `[Elastic Agent]Overview` Dashboard!

### What did you see?

The `[Elastic Agent] Overview` Dashboard is reporting statistics about the total number of agents for the different `host.os.family`.

These panels are **excluding** the `data_stream.dataset: elastic_agent*` (i.e., the monitoring data).

This makes these panels display a wrong number in dedicated monitoring cluster.

### What did you expect to see?

I would expect that the total number of Agents correspond to my fleet or at least to the fleet of agents actually sending the data.

The integration makes also a lot of queries/aggregations in other datastreams to display valuable information and this makes the `[Elastic Agent]Overview` dashboards particularly heavy.

### Anything else?

Please consider that having a dedicated output for monitoring data is supported and even (probably) recommened. Refer to [the documentation](https://www.elastic.co/docs/reference/fleet/agent-policy#change-policy-output).