[java-logging] Logging on GKE has incorrect cluster location

Current logging value for `resource.labels.location` is derived from compute location instead of GKE cluster location. This incorrect value causes us to see no container logs when clicked on "Container Logs" from GKE cluster console UI unless we explicitly remove `resource.labels.location` filter each time when GKE cluster is regional but logs have location value as zonal.

This is fixed in python logging library: https://github.com/googleapis/python-logging/pull/830 by moving to attribute `instance/attributes/cluster-location` from metadata server.

Start in the Java logging library's handling of resource.labels.location and compare it with the linked Python logging change. Trace how metadata-server attributes are read, then verify that regional GKE clusters use instance/attributes/cluster-location and that Container Logs filters resolve correctly.

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