All methods on `PlainEditor` should also be available on `PlainEditorDriver`

The new "driver" API makes sense from an efficiency point of view. But it is super annoying that some methods are only available on PlainEditorDriver and some are only available on PlainEditor. This can be worked around by doing driver.editor., but this is an unnecessary API wart.

I can see two possibilities:

• We manually add all methods
• We implement Deref and DerefMut for PlainEditorDriver