prometheus: Revive the prometheus plugin

[cdecker]

I also added myself as maintainer in the CODEOWNERS file.

[chrisguida]

Excited to see this PR! Will try it out soon :)

[daywalker90]

Tests are flaky, i saw some "address already in use" in one of them.

[chrisguida]

Interesting, looks like this is only broken on 23.11

[chrisguida]

Gonna update the CI to add 24.08 and remove 23.11, then this should be good to go

[chrisguida]

@cdecker any suggestions on how to use this? I'm not familiar with the prometheus protocol.

I think this is fine to merge since this plugin was already in the plugins repo, just archived due to failing tests, which this PR fixes.

ACK 78b17da

[cdecker]

Sure, the plugin just exposes the /metrics URL on a given port (concurrent tests are causing the flakiness), and then you configure your prometheus server to scrape that endpoint, which puts the metrics in its timeseries DB. It's a very lightweight way of collecting metrics in a scalable way.