Navigation Block: Menu item variations should show their corresponding icon

[jasmussen]

When I manually insert a menu item, I choose from this screen:

The "Page Link" is most commonly used (presumably), and is a variation on the Menu Item block. I would expect that icon to also be used for the block after having been inserted. But instead, the "Link" icon is shown:

Can we show the icon that's correct for the variation chosen?

If this is technically not feasible, we should create a generic "Menu Item" icon instead, and show that.

Possibly related: #24814