Add metrics endpoint

[SuperQ]

Add a Prometheus metrics endpoint.

• Expose some srt socket stats.
• Bump minimum Go version to 1.21.
• Update Go build to 1.23.
• Cleanup Makfile.

[SuperQ]

Note, this is just a quick start to get something testable. I don't know much about SRT, so I have only test that this compiles and returns some basic process metrics.

[danimo]

LGTM!

n.b. I'm not a big fan of enabling metrics by default, but that can be remedied by another PR.

[SuperQ]

n.b. I'm not a big fan of enabling metrics by default, but that can be remedied by another PR.

Any specific reason? This implements essentially the same metrics system as is done in the api package HandleStreams() function. The stats are produce by that json API endpoint are stored exactly the same way in Prometheus client_golang, as an atomic.Value.

Only the Prometheus library and format are more efficient for output since it's protbuf/optimized text instead of JSON.

[iSchluff]

Fyi the reason for the strange Makefile is the voc debian package build.
As of this PR that wont work anymore, but I also haven't come up with a good idea yet to solve both debian builds and local builds.

[SuperQ]

Oh, ok. I can take a look at the Debian setup