[Internal]: Fleet Managed Integration Scaling document improvement

### Description

What: Improved documentation to help customers scale without having hundreds of integration policies.
When: As soon as it aligns with resourcing and upcoming Doc releases/updates.
Why: The current documentation does not provide a clear directive on how users can consolidate/minimise the number of integration policies they have to create.

For example, we have customers who wonder if they need to create 200 Oracle integrations to monitor their Oracle DB fleet, as they want to avoid the integration being unhealthy when they set multiple IPs, each of which can only reach itself.

It would be good to have something like [this](https://support.elastic.dev/knowledge/view/2bae10d6) part of the documentation to help customers reduce the number of integrations.

[Internal Slack thread](https://elastic.slack.com/archives/C0JF80CJZ/p1752673722213789?thread_ts=1752669683.337189&cid=C0JF80CJZ) that kicked this off.

### Resources

KB on how to work around this
https://support.elastic.dev/knowledge/view/2bae10d6

### Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

### Feature differences

Affects Both Cloud (stateful + Serveless as users can still deploy their own agents) and On-Prem.

### What release is this request related to?

N/A

### Serverless release

N/A

### Collaboration model

The documentation team

### Point of contact.

**Main contact:** @

**Stakeholders:**