fix: Fix datanode cannot watch channel (#35136)

Panic when `checkWatchedList` failed, this can avoid unnoticed quit of
the channel watch goroutine.

issue: https://github.com/milvus-io/milvus/issues/35135

Signed-off-by: bigsheeper <yihao.dai@zilliz.com>

internal/datanode/event_manager.go

@@ -56,7 +56,7 @@ func (node *DataNode) StartWatchChannels(ctx context.Context) {
 	err := node.checkWatchedList()
 	if err != nil {
 		log.Warn("StartWatchChannels failed", zap.Error(err))
-		return
+		panic(err)
 	}
 	for {
 		select {