Convert OTel resource attributes into trace labels

[CyberHippo]

Is your feature request related to a problem?
As of now, OTel resources attributes are exported to Cloud Trace thanks to #361. However, it is still difficult to filter on service name from the Cloud Trace list interface.

Describe the solution you'd like
Be able to filter on labels derived from exported OTel attributes from the Cloud Trace list interface. Similarly to what has been implemented in Go or Python (see GoogleCloudPlatform/opentelemetry-operations-go#315 and GoogleCloudPlatform/opentelemetry-operations-python#145).

As mentioned in GoogleCloudPlatform/opentelemetry-operations-go#315:

This avoids duplicate timeseries when multiple instances of a service are running on a single monitored resource, for example running multiple service processes on a single GCE VM. Added a config option metric.service_resource_labels to control this.

Describe alternatives you've considered
Adding a default label with the service name to all traces exported to Cloud Trace.

[CyberHippo]

I was mistaking and Otel resource attributes are already converted into labels. I had a rough time using the Cloud Trace filter syntax. I will close this issue.