Bug 1813481 - Allow 'none' keyword in color components r=emilio,supply-chain-reviewers

Make use of the new changes in the cssparser that allows 'none' keywords
in color components where allowed.  We store the none values as 0.0 (as
per the spec) and mark the components with the flags. This way we don't
have to check anything on the components before doing calculations.

As this is the last part intended to be released for the new [color-4]
changes, I've also enabled the changes on nightly.

Differential Revision: https://phabricator.services.mozilla.com/D170208