Parse lab color

Part of the effort to implement CSS Color Module 4.
https://www.w3.org/TR/css-color-4/#specifying-lab-lch

Need to implement override-colors to make font-palette-values-valid.html work.

Per spec, canvas colors are serialized to hex colors when there is no alpha and all other colors should get `rgb` versions. This is not what we were doing in the inspector, etc. I've fixed that here but it means that a lot of tests needed to be rebaselined.

Incidentally solves crbug.com/1300389

wpt tests in the editing/run folder use deprecated features, I'll just mark them as failing. I filed an issue with wpt to get consensus on deleting them:
https://github.com/web-platform-tests/wpt/issues/35662

Bug: 1354622, 1300389
Change-Id: I3ea141144b2797f2ebc9f2b98ba0c1da54257879
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3836777


Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Aaron Krajeski <aaronhk@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1040970}