style: Implement :-moz-any() as an alias of :is().
style: Implement :-moz-any() as an alias of :is().

This is strictly better and more flexible, but can change specificity so
have a pref in case it causes trouble. I doubt it will though, the
specificity rules of :is() make more sense, and my gut feeling is that
:-moz-any is not very used on the wild.

Make it early-beta-or-earlier for now to minimize risk, once this is on
nightly for a bit we can enable it everywhere.

Differential Revision: https://phabricator.services.mozilla.com/D86696

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