Clean up Windows testsuite failures

Summary:
Another round and attempt at getting these down to 0.

We really should re-enable the CI and not wait for those cloud based ones.

I've disabled the backpack tests on windows as they are too broad, they test
as much the shell as they do the compiler.

The perf tests have been too long to track down. but the numbers are horrible
but I don't see them getting fixed so just have to accept them.

T9293 has new windows specific output because a Dyn way only flag was added.
This will of course not work on non-Dyn way builds.

Test Plan: ./validate

Reviewers: bgamari, hvr, simonmar

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #15107

Differential Revision: https://phabricator.haskell.org/D4668