* Add buttons to WidgetController and TestPointer

* Add more buttons

* Let TestPointer handle default device

* Use getter only buttons

Instead of using a custom WidgetController, which is very brittle, we just use the usual infrastructure.

Also, use structured data instead of an array.

This adds offsetMoreOrLessEquals to handle small floating point errors in offsets.

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

Breaks the moveBy call from drag and dragFrom into two separate calls and changes the default behavior of DragStartBehavior to DragStartBehavior.start (#26438)

* Breaking change which sets the default DragStartBehavior to DragStartBehavior.start and changes WidgetTester.drag and WidgetTester.dragFrom by breaking the moveBy function call into multiple pieces.