feat: stamp Queue shard status with availability zones

Resolves each shard topic's replica broker IDs (internal/kafka.Admin.
ReplicaBrokerIDs) to the topology.kubernetes.io/zone labels of the nodes
hosting those brokers (ZoneLocator), and writes the result into
ShardStatus.AvailabilityZones each reconcile. Uses mgr.GetAPIReader()
rather than the cached client for the Pod/Node lookups, since the cached
client would otherwise require cluster-wide list/watch RBAC on Pods just
to serve occasional point Gets.

internal/operator/admin.go

@@ -13,4 +13,5 @@ type TopicAdmin interface {
 	DeleteTopic(ctx context.Context, topic string) error
 	LogEndOffsetSum(ctx context.Context, topic string) (int64, error)
 	ConsumerLag(ctx context.Context, group, topic string) (int64, error)
+	ReplicaBrokerIDs(ctx context.Context, topic string) ([]int32, error)
 }