atecontroller: serve ate.workerpool.* on :8080 when also pushing #2402

With OTEL_METRICS_EXPORTER unset or otlp,prometheus, :8080 serves only the controller-runtime families. The ate.workerpool.* instruments are pushed but not served, so these values do not yet follow the policy in #2067. Registering them on the controller-runtime registry would make the OTLP bridge push them twice.

Follow-up to #1976.