ui: fix replication lag metric for multinode clusters and cutover

Replication lag metric would report absurdly high lag for multinode
clusters as it would take the average of the reported timestamps, and as
some nodes may report 0, this would cause extremely low replicated
times. Patched by taking the highest replicated time of all the nodes.
Also stop reporting replication lag when ingesting has stopped (e.g.
cutover or job cancel/fail).

Informs cockroachdb#120652

Release note (ui change): fix replication lag metric reporting for multinode
clusters and cutover

pkg/ccl/streamingccl/streamingest/stream_ingestion_job.go

@@ -510,12 +510,13 @@ func maybeRevertToCutoverTimestamp(
 	if p.ExecCfg().StreamingTestingKnobs != nil && p.ExecCfg().StreamingTestingKnobs.OverrideRevertRangeBatchSize != 0 {
 		batchSize = p.ExecCfg().StreamingTestingKnobs.OverrideRevertRangeBatchSize
 	}
+	p.ExecCfg().JobRegistry.MetricsStruct().StreamIngest.(*Metrics).ReplicatedTimeSeconds.Update(0)
 	if err := revertccl.RevertSpansFanout(ctx,
 		p.ExecCfg().DB,
 		p,
 		remainingSpansToRevert,
 		cutoverTimestamp,
-		// TODO(ssd): It should be safe for us to ingore the
+		// TODO(ssd): It should be safe for us to ignore the
 		// GC threshold. Why aren't we?
 		false, /* ignoreGCThreshold */
 		batchSize,

pkg/ui/workspaces/db-console/src/views/cluster/containers/nodeGraphs/dashboards/crossClusterReplication.tsx

@@ -58,7 +58,7 @@ export default function (props: GraphDashboardProps) {
       <Axis units={AxisUnits.Duration} label="duration">
         <Metric
           downsampler={TimeSeriesQueryAggregator.MIN}
-          aggregator={TimeSeriesQueryAggregator.AVG}
+          aggregator={TimeSeriesQueryAggregator.MAX}
           name="cr.node.physical_replication.replicated_time_seconds"
           title="Replication Lag"
           transform={datapoints =>