Add service.* resource attributes to metrics labels

[aabmass]

This prevents writing duplicate timeseries from different processes when they correspond to the same monitored resource. For example, three processes on the same gce_instance VM need a label to distinguish them.

We already do this in the collector exporter as we have specced out.

[aabmass]

Need to work on this before the stable metrics exporter release.

[Le-G]

While this is implemented, is there a way to include those service resource labels (or any other unique id) in the metrics labels other than manually adding them to the metric labels ?
Not having this causes duplicates when sending metrics concurrently.

[aabmass]

You'd have to add them manually for now unfortunately.

[aabmass]

We'd probably want to implement it as a configurable option with a default, similar to how the Golang exporter does it https://github.com/GoogleCloudPlatform/opentelemetry-operations-go/blob/3e654c04a79bd43915e5e47f71213e868799ff92/exporter/metric/option.go#L46-L49

[aabmass]

Leaving this up for grabs as I still don't have time to work on it.