[9.0] (backport #18082) Fix gauge type correctly where requesting pipeline metrics in condition.

[mergify]

Release notes

A fix to receive gauge metric types in pipeline info which appears in pipeline vertex of node stats API.

What does this PR do?

Why is it important/What is the impact to the user?

Checklist

• My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

• pull this change and build Logstash
• Use elastic-agent input plugin (whose current_connections and peak_connections are gauge/number) in your pipeline
• call GET localhost:9600/_node/stats?graph=true&vertices=true API
• Check the response that

Related issues

Use cases

• Visualizations or monitoring tools which aligns on node stats API's vertex info

Screenshots

Logs

 "vertices": [
                {
                    "id": "input-agent",
                    "pipeline_ephemeral_id": "6fc8016a-de9f-42d9-ba38-6aed98d4ab92",
                    "double_gauges": [. // <----------- THIS WASN'T EXIST BEFORE
                        {
                            "name": "current_connections",
                            "value": 1
                        },
                        {
                            "name": "peak_connections",
                            "value": 3
                        }
                    ],
                    "queue_push_duration_in_millis": 0,
                    "events_out": 6
                },
                ...
]
```<hr>This is an automatic backport of pull request #18082 done by [Mergify](https://mergify.com).

[mashhurs]

LGTM!

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
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[elasticmachine]

💚 Build Succeeded

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• Commit: e4b71ef

cc @mashhurs