Unable to interrupt kernel while debugging a notebook cell

[joyceerhl]

Testing microsoft/vscode#133905

The test plan item suggests it's possible to interrupt the kernel while debugging a cell, but the interrupt kernel button is disabled while debugging:

[roblourens]

You can click the stop button on the cell, but I'm not sure why the notebook-level one is disabled. It is contributed by the jupyter extension and the kernel is probably not busy at this moment, so this is probably related to #7661