Check if we need batch types

[scofalik]

Undo introduces and uses two batch types at the moment: undo and redo batch types. They are needed for proper integration between commands and between deltas incoming from different sources.

I hope that we can at least get rid of redo batch and maybe even undo batch if we can use events fired by UndoCommand and RedoCommand and change undo/redo algorithm a bit. It was doable before but there were some problems with selection and ultimately it was easier for me to use batch types. But for me, batch types should be more general and having undo and redo batch types feels very bad.

[pjasiun]

Closed via ckeditor/ckeditor5-undo#14 and ckeditor/ckeditor5-engine#499.