gui, lib/model: Display list of files needed by remote (fixes #4369)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4559
LGTM: AudriusButkevicius, calmh

cmd/syncthing/summaryservice.go

@@ -211,6 +211,7 @@ func (c *folderSummaryService) sendSummary(folder string) {
 			"device":      devCfg.DeviceID.String(),
 			"completion":  comp.CompletionPct,
 			"needBytes":   comp.NeedBytes,
+			"needItems":   comp.NeedItems,
 			"globalBytes": comp.GlobalBytes,
 		})
 	}