Survey existing metrics definitions across existing libraries

From the meeting notes where this action item was created:

- Lower level Telemetry.Metrics interface in Erlang
- Currently using Structs and Protocols, so hard to convert to Erlang
- Docs might not be as good
- Intention with Phoenix 1.5 is to include this by default, so might not be as seamless
- The API needs to be really good because end-user developers are going to interact with it; not just library authors
- Main issue is with reporters, because if the internal data structures are different, they’d need to support both - need some kind of abstraction that both can handle (like maps)
- How will this interact with OpenTelemetry’s metrics feature set? Probably a lot of overlap, so we need to make sure that it’s not too confusing for people.
- Action: Arkadiusz to Survey existing metrics definitions across existing libraries (Prometheus, OpenCensus, Statix, Telemetry.Metrics) before next meeting