Summary:
This patch is a refinement of the original commit (which
was reverted):

  commit 6b976eb8
  Date:   Fri Jan 13 08:56:53 2017 +0000
      Record evaluated-ness on workers and wrappers

In Trac #13027, comment:20, I noticed that wrappers created after
demand analysis weren't recording the evaluated-ness of strict
constructor arguments.  In the ticket that led to a (debatable)
Lint error but in general the more we know about evaluated-ness
the better we can optimise.

This commit adds that info
  * both in the worker (on args)
  * and in the wrapper (on CPR result patterns).
See Note [Record evaluated-ness in worker/wrapper] in WwLib

On the way I defined Id.setCaseBndrEvald, and used it to shorten
the code in a few other places

Then I added test T13077a to test the CPR aspect of this patch,
but I found that Lint failed!

Reason: simpleOptExpr was discarding evaluated-ness info on
lambda binders because zapFragileIdInfo was discarding an
Unfolding of (OtherCon _).  But actually that's a robust
unfolding; there is no need to discard it. To fix this:

* zapFragileIdInfo only zaps fragile unfoldings

* Replace isClosedUnfolding with isFragileUnfolding (the latter
  is just the negation of the former, but the nomenclature is
  more consistent).  Better documentation too
       Note [Fragile unfoldings]

* And Simplify.simplLamBndr can now look at isFragileUnfolding
  to decide whether to use the longer route of simplUnfolding.

For some reason perf/compiler/T9233 improves in compile-time
allocation by 10%.  Hooray

Nofib: essentially no change:

--------------------------------------------------------------------------------
        Program           Size    Allocs   Runtime   Elapsed  TotalMem
--------------------------------------------------------------------------------
      cacheprof          +0.0%     -0.3%     +0.9%     +0.4%     +0.0%
--------------------------------------------------------------------------------
            Min          +0.0%     -0.3%     -2.4%     -2.4%     +0.0%
            Max          +0.0%     +0.0%     +9.8%    +11.4%     +2.4%
 Geometric Mean          +0.0%     -0.0%     +1.1%     +1.0%     +0.0%