Logo variant override is available for 'wordmark' and 'tagline' in
the new Vector skin and has been used for a while, but the 'logo'
feature built in the core didn't take variants into account.
The logic should be pushed down to ResourceLoaderSkinModule so that
behavior can be consistent between skins and core.
Also, old code use $title->getPageViewLanguage() to determine the
variant of logo, which is a wrong behavior. Logos should be in the
interface language instead of the content variant.
Bug: T273578
Change-Id: Ifb3cc45600d57cf9c72757016148684cd7ab1400
fbe6443942