enabled core cell delete for IW and undo operations

[amunger]

microsoft/vscode-jupyter#7756

• Check if an operation should be placed on the undo stack, rather than checking if undo is available at all
  • The interactive window is a partially read-only notebook, and delete cell is an exception since it can be performed by the user. We want to enable undo for that operation
• deleting a cell while having focus elsewhere requires first focusing on the history, but doesn't always work depending on which component was actually given focus (out of scope issue)
• Also stopped some maintenance code from being placed on the undo stack (reset)

[amunger]

this was strange and feels like it should be false. It's only called on creation of notebooks as far as I could tell: Create a notebook, ctrl+z - a no-op undo is performed

[rebornix]

It would be great if @jrieken can help take a look at the change in how applyEdits is changed.

[amunger]

@jrieken - any feedback on the changes here?