Expose basic Autoscaling metrics

[samos123]

autoscaling metrics.. things like number of qps per replica, number of replicas, autoscaling time (e.g. time from pod request to pod ready)

[nstogner]

Note: KubeAI already exposes a metrics endpoint with some boring metrics. We just need to add these to that endpoint.

NOTE: Alex made a contribution to Lingo that can be used as a reference: b476ca2

[nstogner]

We should do this with OpenTelemetry as that appears to be the way everything is heading.

[alpe]

👍 if this is not super urgent, I would work on this later this week.

[nstogner]

Hey @alpe - I’ve started on this one already. I forgot to assign it. Would love a review from you though!