Add missing metrics and labels to Prometheus emitter

[TessaIO]

Description

Some of the metrics on the Prometheus emitter are missing, and some lack labels.
The ones that are missing are basically the ones added in this PR.
The one that is missing a label is service/heartbeat and it's missing the dimension (label) leader.

Motivation

Currently, we're passing our custom metrics.json to the prometheus emitter, and each time we do an upgrade, we need to also to make sure to update that file, which sometimes can be tedious from an operational point of view to do it on each upgrade. It would be nice if we could include these dimensions and metrics in the JSON file in the upstream.

[TessaIO]

If the request makes sense, feel free to assign it to me

[gianm]

A PR to update the file in our own distribution would be great. It doesn't always get updated with every new metric. If you're interested, please feel free to do it and link the PR to this issue.