changefeedccl: add more verbose logging around schema changes

This patch adds more verbose logging to the change aggregator around
receiving and emitting resolved spans to help debug recurring changefeed
schema change test flakes.

Release note: None

Author: andyyang890

pkg/ccl/changefeedccl/changefeed_processors.go

@@ -867,6 +867,10 @@ func (ca *changeAggregator) flushBufferedEvents() error {
 // changeAggregator node to the changeFrontier node to allow the changeFrontier
 // to persist the overall changefeed's progress
 func (ca *changeAggregator) noteResolvedSpan(resolved jobspb.ResolvedSpan) (returnErr error) {
+	if log.V(2) {
+		log.Infof(ca.Ctx(), "resolved span from kv feed: %#v", resolved)
+	}
+
 	if resolved.Timestamp.IsEmpty() {
 		// @0.0 resolved timestamps could come in from rangefeed checkpoint.
 		// When rangefeed starts running, it emits @0.0 resolved timestamp.
@@ -950,6 +954,9 @@ func (ca *changeAggregator) emitResolved(batch jobspb.ResolvedSpans) error {
 			RecentKvCount: ca.recentKVCount,
 		},
 	}
+	if log.V(2) {
+		log.Infof(ca.Ctx(), "progress update to be sent to change frontier: %#v", progressUpdate)
+	}
 	updateBytes, err := protoutil.Marshal(&progressUpdate)
 	if err != nil {
 		return err