Rename Drawable::boxed to into_element and make containers generic

Multi-element are now generic over any drawable child, which can be converted
into an element.

Co-Authored-By: Nathan Sobo <nathan@zed.dev>
Co-Authored-By: Max Brunsfeld <max@zed.dev>
03619dfa55Antonio Scandurra committed on 4/21/2023, 6:43:19 PM· committed by Nathan Soboparent4d43366
64 files changedLine totals unavailable