kvclient/rangefeed: release resource properly for restartActiveRangeFeeds

Previously, resources were not properly released when restartActiveRangeFeeds
returned early due to an error, without calling restartActiveRangeFeed on each
toRestart rangefeed. This commit fixes the resource leak.

Fixes: #129486
Release note: none

Author: wenyihu6

pkg/kv/kvclient/kvcoord/dist_sender_mux_rangefeed.go

@@ -529,8 +529,12 @@ func (m *rangefeedMuxer) receiveEventsFromNode(
 func (m *rangefeedMuxer) restartActiveRangeFeeds(
 	ctx context.Context, reason error, toRestart []*activeMuxRangeFeed,
 ) error {
-	for _, active := range toRestart {
+	for i, active := range toRestart {
 		if err := m.restartActiveRangeFeed(ctx, active, reason); err != nil {
+			// Release all remaining rangefeeds that we won't restart.
+			for _, remaining := range toRestart[i+1:] {
+				remaining.release()
+			}
 			return err
 		}
 	}