Core CSS support for root padding and alignfull blocks

[bgardner]

Per Gutenberg 13.8: WordPress/gutenberg#42085

[bgardner]

@ndiego I noticed that Carolina added this section to FSE.com which might be handy: https://fullsiteediting.com/lessons/theme-json-layout-and-spacing-options/#h-padding-aware-alignments

[ndiego]

This has been implemented, but additional testing is warranted before including in a release.

[richtabor]

Did you two notice anything happening like this? WordPress/gutenberg#43095

[ndiego]

@richtabor yeah, there are some quirks. I added some notes to your ticket.

[bgardner]

Reopening given there appears to be an issue at hand.