These should fix #7024 and #7022, among others.

The main difficulty was that we were getting occ-name clashes
between kind and type variables in TyCons, when spat into an
interface file. The new scheme is to tidy TyCons during the
conversoin into IfaceSyn, rather than trying to generate them
pre-tidied, which was the already-unsatisfactory previous plan.

There is the usual wave of refactorig as well.