PrometheusReceiver Configuration - Deprecate `ReportExtraScrapeMetrics`

[ArthurSens]

Component(s)

receiver/prometheus

Describe the issue you're reporting

When enabled, extra metrics that bring information about the scrape will be included. This is an option because such behavior is considered an experimental feature in Prometheus.

As noted in a related issue (#44196), a Stable component needs to be observable by default, and several important metrics related to the scrape behavior are only available if ReportExtraScrapeMetrics is set to true. That sparks the question: Should this be false by defalt? Should this even be configurable?

The reason why it's configurable today is because the feature itself is considered experimental in Prometheus upstream, and might be removed without prior notice.

This issue is being created to start discussion on how to proceed. Should we work with Prometheus upstream to stabilize this feature? Should we keep things as they are?

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[github-actions]

Pinging code owners:

• receiver/prometheus: @Aneurysm9 @dashpole @ArthurSens @krajorama

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[ArthurSens]

Discussing this briefly with @dashpole, we believe ReportExtraScrapeMetrics should not be a configuration option, but rather a feature flag, as it is also a feature flag in Prometheus. If the feature flag is promoted upstream, we promote it here. If it's deprecated and removed, we remove it here.