The 3 important hooks run inside SkinTemplate should be run inside Skin on the long term so subclasses of Skin can use them.
When we introduce a SkinMustache class ideally it would subclass Skin rather than SkinTemplate but to make its introduction easier we made it extend SkinTemplate
# precursors
[] T262098 is resolved
[] T262730 is resolved
[] T255319 is resolved
[] T259313 is resolved
# Acceptance criteria
[] Skin::getFooterLinks is promoted from SkinTemplate.php to Skin.php. The hook SkinAddFooterLinks is not impacted by this move as it already uses the skin and currently only lives in that class for compatibility reasons.
[] buildContentNavigationUrl is promoted to SkinTemplate and The SkinTemplateNavigation::Universal hook is modified to run with a Skin instance instead of a SkinTemplate.
[] buildContentNavigationUrls is moved from SkinTemplate to Skin
[] PersonalUrls is moved from SkinTemplate to Skin and the PersonalUrls hook is modified to run with a Skin instance instead of a SkinTemplate.
[] SkinMustache extends Skin not SkinTemplate