Refactor: EditableTextView.Changed() and the Canceled spelling

EditableTextView.Changed is a method like every other result's.
AlertDialogResult, PopconfirmResult and DateTimeResult spell Canceled
the American way, matching EditableTextView and LoadingOverlayResult.
Callers, Gallery and docs updated.

docs/components/056-date-time-picker.md

@@ -47,7 +47,7 @@ ui.Render(view, 400, 300, 1)
 
 ## 事件
 
-`Changed()`：确认且时刻改变时为 true，写入的值位于 `Location`。`Cancelled()`：取消、Escape 或点击外部关闭时为 true。
+`Changed()`：确认且时刻改变时为 true，写入的值位于 `Location`。`Canceled()`：取消、Escape 或点击外部关闭时为 true。
 
 ## 键盘操作