list: restructure the component

[crisbeto]

As discussed with @ThomasBurleson, we should try to simplify the list component at some point, because it shuffles the DOM a lot and is overly complicated. This can lead to issues like #6152 and #8172.

[devversion]

@crisbeto - Elad and I already worked on that.

We started with a design doc, but this refactoring was currently pushed back in the queue, because there were other priorities.

[crisbeto]

Ah cool, is there an issue for it so I can reference it in the ones?

[devversion]

There is no issue yet, so I think it's good to use your issue now.

• mdListItem: some styling issues #7742 (comment)