The CSSWG resolved that `block-size: stretch` on a block-level box
stretches the margin box to fill the parent. However, if the parent
doesn't have padding nor border, and doesn't establish an independent
formatting context, then we assume that the margins will collapse.
Therefore, we treat the margins as zero when resolving the stretch size,
regardless of whether they will actually end up collapsing.
https://github.com/w3c/csswg-drafts/issues/11044#issuecomment-2599101601https://drafts.csswg.org/css-sizing-4/#stretch-fit-sizing
Signed-off-by: Oriol Brufau <obrufau@igalia.com>
