GKE Resource detection doesn't work well with workload identity

[dashpole]

Describe the bug

Create a GKE cluster with workload identity enabled. Try using the GCE resource detector. It produces error messages because of missing fields. Try to use the GKE resource detector instead. Now you are missing important resource information.

The GKE resource detector should set zone/region based on the cluster-location metadata attribute instead.

[dashpole]

In general, the GKE resource detector should only set one of [zone, region] since a cluster with the same name can exist in both zonal and regional form within the same project.

[dmitryax]

@dashpole do we have someone who can on this?

[dashpole]

I plan to work on this as soon as I can find time.