Better update path for existing sites using layout builder

I agree that the option B is better. There really is no need for additional config checkmark, it was the first thing that popped into my mind when I was thinking about the PR.

The code looks good. I added a cosmetic comment to display the actual ids of the ce displays that were changed instead of count.

Thanks! Yeah outputing IDs would be nicer, happy to improve if someone wants to submit a follow-up.
I rather move on with it now, since current MR is already successfully tested.