Communicate more clearly when a synced pattern has unsaved changes (in the canvas).

[mtias]

Extracted from tracking issue

I think the simplest form of this could be a blue dot in the block icon in the toolbar, list view, and inspector control.

[talldan]

There was a previous PR that was close to being merged - #32464

Some parts of that could be extracted. I don't think the contributor was available to work on it any more.

[youknowriad]

Given how the block behaves today. Clicking "Edit original" to go to a separate focused view to edit the pattern, do you think this is still valuable?