Simplify lintIdUnfolding

Authored by mpickering on Fri, Jul 6, 10:00 AM.

Description

Simplify lintIdUnfolding

The logic for DFunUnfolding seemed quite confusing and unecessary. A
simpler strategy uses maybeUnfoldingTemplate, as that is what is
actually used when doing inlining and checking that has the right type.

Reviewers: simonpj, goldfire, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4919