Whether the newWidget can be used to update an Element that currently
has the oldWidget as its configuration.
An element that uses a given widget as its configuration can be updated to
use another widget as its configuration if, and only if, the two widgets
have runtimeType and key properties that are operator==.
Source
static bool canUpdate(Widget oldWidget, Widget newWidget) {
return oldWidget.runtimeType == newWidget.runtimeType
&& oldWidget.key == newWidget.key;
}