lib/config, lib/model: Tweaks to the auto accept feature

Fix the folder restart behavior (ignore Label), improve the API for that
(imho).

Also removes the tab switch animation in the settings modal, because
annoying.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4577

lib/util/utils.go

@@ -87,6 +87,11 @@ func CopyMatchingTag(from interface{}, to interface{}, tag string, shouldCopy fu
 		fromField := fromStruct.Field(i)
 		toField := toStruct.Field(i)
 
+		if !toField.CanSet() {
+			// Unexported fields
+			continue
+		}
+
 		structTag := toType.Field(i).Tag
 
 		v := structTag.Get(tag)