We also need to update `stgBindHasCafRefs` assertion with this change,
as we no longer have the pre-computed SRT, LiveVars etc. We rename it to
`topStgBindHasCafRefs` and implement it like this:

A non-updatable top-level binding may refer to a CAF by referring to a
top-level definition with CAFs. A top-level definition may have CAFs if
it's updatable. At this point (because this is done after TidyPgm)
top-level Ids (whether imported or defined in this module) are
GlobalIds, so the top-levelness test is easy. (see also comments in the
code)

Reviewers: bgamari, simonpj, austin

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1889

GHC Trac Issues: #11550