Reimplement aliases in geom

The alias needs to be part of the provider instead of the geom to work
properly. To bind the DEV geom, we need to look at the provider's names and
aliases and create the dev entries from there. If this lives in the GEOM, then
it won't propigate down the tree properly. Remove it from geom, add it provider.

Update geli, gmountver, gnop, gpart, and guzip to use it, which handles the bulk
of the uses in FreeBSD. I think this is all the providers that create a new name
based on their parent's name.