Refactor Layers UI to use DnDKit

I marked 3 Layers menu related bugs as postponed on this issue. Hopefully migrating to dndkit fixes those bugs. If not, let's re-open the bugs that don't get fixed by the dndkit switch.

MR !1024 is now ready for review.

MR !990 is now over at 📌 Refactor sortable props form in code component editor Active

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Amazing work on this @jessebaker 👏