This PR:

• is a partial fix for Notebook diff revert icon can't be disabled #165189 - the arrows now won't show up in the notebook diff view. This is a fixed behavior, regardless of what the user setting is, following the existing example of other notebook diff configs.
• addresses the issue that arrows show up even when the right-hand-side editor is readonly (not sure if this is mentioned in an issue before).
• addresses the issue that sometimes an arrow reverts the wrong deleted block (not mentioned in an issue before as far as I know), please see following gifs for demo:

Before fix:

After fix:

CC @hediet

I think these are small fixes, but please let me know if I should create additional issues for them, or if anything needs to be fixed / improved in the code. Thanks!