Updates the design of the alignment dropdown to include "none" as an option (it's the same as unsetting). The center icon has been updated, and the previous icon for centering has been repurposed for indicating "None". There's help text for "None" and "Wide", to show the values for the content and wide area layout values.

For themes that do not support wide or fullwide alignments we render some contextual text to clarify the missing buttons: