Replaces hardcoded color hex values with their equivalent
values from Codex, via the "mediawiki.skin.variables" system.
Bug: T366197
Change-Id: Ia929a1a8d6351222acb454c8ec750e920ae6d072
In MediaWiki, OO.ui.getTeleportTarget() is overridden to return
a different element (itself attached to body), which is supposed
to be styled appropriately by skins (e.g. z-index above any
floating header, font-size same as body text, etc.).
As a result, we no longer need to do weird things with the
'vector-body' class to achieve correct font size on Vector,
and we can remove some font-size overrides for Vector and MonoBook.
Bug: T348288
Bug: T339058
Change-Id: I6329b3023573b3dcfc8f471c4693be9bb1e9e430