fix(prometheus_remote_write source): Interpret metrics ending with _total as counters

[AyseGokmen]

Summary

This PR aims to align the actual behavior of prometheus remote write source to documentation.

For metrics named with a suffix of _total, this source emits the value as a counter metric. All other metrics are emitted as gauges.

References

Related: #22825

Vector configuration

[sources.prometheus_rw]
type = "prometheus_remote_write"
address = "0.0.0.0:9095"

[transforms.filter_test_metrics]
type = "filter"
inputs = ["prometheus_rw"]
condition = '''
starts_with(string!(.name),"http")
'''

[sinks.file_sink]
type = "file"
inputs = ["filter_test_metrics"]
path = "/tmp/metrics.json"

[sinks.file_sink.encoding]
codec = "json"

[sinks.console_output]
type = "console"
inputs = ["filter_test_metrics"]
encoding.codec = "json"

How did you test this PR?

I have created a docker compose environment with prometheus, vector and node_exporter. Prometheus gathers some counters node_exporter is exposing. Prometheus is configured to send to vector prometheus_remote_write source. Vector then prints received metrics into a file and console.

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

Contributor Guidelines

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[github-actions]

All contributors have signed the CLA ✍️ ✅
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[AyseGokmen]

I have read the CLA Document and I hereby sign the CLA

[thomasqueirozb]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: 72a43a9270

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[AyseGokmen]

Should I create a changelog for this? I am hesitant because it is already a documented behavior.