Don't unpack wheels during preparation
Don't unpack wheels during preparation

For some time we have not needed to pre-emptively unpack wheels as part
of metadata processing, but kept the existing logic because the
behavior would start to diverge more for different package types. In
this case, though, removing the special cases for wheels makes this
logic a bit simpler, so it is worth doing.

pfmoore/pip,pypa/pip,sbidoul/pip,pfmoore/pip,pradyunsg/pip,sbidoul/pip,pradyunsg/pip,pypa/pip