interfaces: make the world simpler #5540
interfaces: make the world simpler #5540

Make a few assumtions about complexity:

1. We can stack bridges on top of GREs stacked on top of GIFs.
2. We do not stack any virtual device on itself.
3. VIP handling in GIF/GRE is ok to coalesce if we simply create
   VIPS before we start doing GIF/GRE.  Bridges follow GIFs as before.
5. The reason we create unassigned devices is to assign them via GUI.
6. We do not need to run inline device creation when we assure they
   are already there before we configure.

opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core