Fix GHCi space leaks (Trac #15111)
Summary:
There were a number of leaks causing previously loaded modules to be
retained after a new :load. This fixes enough leaks to get the
tests to pass from D4658.
Test Plan: See new tests in D4658
Reviewers: niteria, bgamari, simonpj, erikd
Subscribers: thomie, carter
GHC Trac Issues: Trac #15111
Differential Revision: https://phabricator.haskell.org/D4659