Changes:
- Add the LatestSkinVersionRequirement requirement class, which lazily
evaluates the application state to get the version of the skin for the
request.
This majority of this class is taken from Stephen Niedzielski's
Vector\SkinVersionLookup class, which was introduced in d1072d0fdf.
- Register an instance of LatestSkinVersionRequirement and register the
'LatestSkin' feature that requires that requirement
- Re-introduce SkinVector::isLegacy and make it defer to the Feature
Manager
Bug: T244481
Change-Id: If6b82a514aa5afce73e571abdd8de60b16a62fa8
