Add Integrations Server to monitoring docs

[kilfoyle]

Summary

This updates:

• the View monitoring data in Kibana section of the "Access monitoring data in Kibana" page, to update the graphic so that it includes the Integrations Server section.
• the Visualizing monitoring data page, to add a link for Integrations Server

And it adds a page:

• Integrations Server metrics

Closes: #1243

@eedugon (or anyone familiar with ECK deployments), I've marked the new Integrations Server metrics page as unavailable for ECK. Would you happen to know if that's correct? It seems like ECK doesn't have an Integrations Server in the way that the other deployment types do, but please correct me if I'm wrong. I'm not sure how I can easily test that.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

Tool(s) and model(s) used: I used Gemini to try and find out if Integrations Server is included in ECK deployments, and specifically ECK monitoring.

[github-actions]

✅ Vale Linting Results

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[github-actions]

🔍 Preview links for changed docs

• deploy-manage/monitor/monitoring-data/integrations-server-page.md
• deploy-manage/monitor/monitoring-data/visualizing-monitoring-data.md
• deploy-manage/monitor/stack-monitoring/kibana-monitoring-data.md

[shainaraskas]

I'm 99% sure that integrations server is ECH/ECE only

initial request backs this up, as do the integration server docs results

[kilfoyle]

Thanks @shainaraskas! I've updated the labels to indicate ECE and ECH only for Integrations Server monitoring.

[shainaraskas]

couple of suggestions around helping people to contexualize what an integrations server / apm server is, one small style suggestion

[kilfoyle]

Thanks @shainaraskas. I reworked the page. Please have another look when you can.

[eedugon]

LGTM!
As you have noted:

{{integrations-server}} is available in {{ech}} and {{ece}} deployments as a combined offering of Application Performance Monitoring (APM) Server and Fleet Server.

That's perfect.
On ECK, Fleet Server and APM server (binary or as past of Elastic Agent) can deployed independently.

One interesting thing that we could research in the scope of a new issue is what happens for STACK MONITORING in self-managed & ECK deployments when we enable monitoring of Fleet Server and APM Server. Because I'm pretty sure Stack Monitoring should show the metrics and I'm not sure under what "label" or "section" they will be.

I wouldn't be surprised if they end up also in the "integrations server" area. But anyway I think this PR is perfect with the current information we know.