Orienting on Codex Opacity tokens as defined in v10 of 2022-04-01 in
https://www.figma.com/file/h9pA2CCl2i0wtlTKNChaES/Opacities---Tokens?node-id=368%3A2139
Also adding legacy opacity icon tokens for use in all non-Codex
products.
Specifically the icon ones are already in use in Vector.
Bug: T317800
Change-Id: Ib699ccf0342030f521ad876d70974b8818f877cb
Follow Web Content Accessibility Guidelines and
use Wikimedia Design Style Guide colors with
at least 3:1 contrast with surrounding body text.
Also unify external and normal links as the color difference is
basically opaque to understand beyond a small group of power users.
Bug: T213778
Bug: T315321
Change-Id: I8a309eedd70b9a82fcca91c2cf9a30beea602b6b