Miscellanous compliance fixes

[gagbo]

Description

• Rename function_calls_count to function_calls
• Update autometrics-shared
• Add unit to histogram duration
• Replace caller with caller.(function|module)
• Add service.name label

Fixes #54
Fixes #60
Fixes #62

Checklist

• The CHANGELOG is updated.
• The open-telemetry example in repository works fine:
  • the docker compose file is valid
  • the application compiles and run
  • alerts are getting triggered in Prometheus
• The prometheus example in repository works fine:
  • the docker compose file is valid
  • the application compiles and run
  • alerts are getting triggered in Prometheus
  • exemplars are accessible on the graph

[gagbo]

The SLO-breach reporting is broken for multiple reasons:

• the refactoring to use context.Context brought a regression on latency detection (see ffafd90 )
• the rules file from autometrics-shared isn't updated to detect error rate correctly with the new function calls metric name and the new function duration metric name (see this comment)

So the PR is currently blocked

[gagbo]

Update: the error rate alert has been fixed, but there's still a typo in the latency query, once that is solved (and the bundled rules get regenerated) it's being merged