Sort factors of a product node during simplication
When we simplify a product node, sort the factors according to the spec.
https://drafts.csswg.org/css-values/#calc-serialize
Some tests that assume the factors stay in the declared order is fixed.
Differential Revision: https://phabricator.services.mozilla.com/D225626
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1924679
gecko-commit: 28e8c3437cef60d9b07e32c73f70a4f454ea66ef
gecko-reviewers: layout-reviewers, jfkthame