Incorrect undo/redo action on notebook editors

[msujew]

Bug Description:

Our logic to capture undo/redo is pretty outdated and doesn't work correctly in a lot of cases. One of the examples is listed in the reproduction steps.

Steps to Reproduce:

1. Open a normal text document and change something to make it dirty
2. Open a notebook editor and add a new cell
3. Defocus the notebook editor cell and run the undo action. It will undo the changes in the text document instead of removing the new cell.

Additional Information

• Theia Version: 1.52