[exporter/zipkin] Support scope attributes

[mx-psi]

Component(s)

exporter/zipkin

Is your feature request related to a problem? Please describe.

The Zipkin exporter currently ignores the scope attributes on OTLP payloads. This leads to missing information and we have a repo-wide initiative to support scope attributes, see #38744

Describe the solution you'd like

Scope attributes are added as tags, having precedence over resource attributes but being overwrritten by span attributes with the same name (to be consistent with how we add resource attributes).

We should take open-telemetry/opentelemetry-specification/issues/4473 into account to make sure we have a consistent behavior across implementations.

Describe alternatives you've considered

Alternatively, resource and scope attributes can be added under a particular namespace that is reserved for attributes of a particular type. There is precedent for this on the Prometheus mapping.

Additional context

Also relates to open-telemetry/opentelemetry-specification/issues/2535

[github-actions]

Pinging code owners:

• exporter/zipkin: @MovieStoreGuy @andrzej-stencel @crobert-1

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[andrzej-stencel]

This should be implemented in /pkg/translator/zipkin/zipkinv2/from_translator.go, as this is what is used by the Zipkin exporter: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/v0.126.0/exporter/zipkinexporter/zipkin.go#L19.

To be more specific, the extraceScopeTags function should go through the scope attributes and add them as zipking tags in zTags map, similar to what the function resourceToZipkinEndpointServiceNameAndAttributeMap is already doing for resource attributes.