Make HarfBuzz-NG the default shaper on all platforms

[ChangeLog][Important Behavior Changes] HarfBuzz-NG is now the default
shaper on all platforms. This results in a better shaping results
for various languages, better performance, and lower memory consumption.

Task-number: QTBUG-18980
Change-Id: I4d9454fc37e9050873df3857e52369dfc7f191b2
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Skip the expose region test on Windows

In some CI configurations this fails from time to time. Have to disable
it unless we can make it more robust somehow.

Change-Id: Iadd8904d7223a6aeff53dafa36b94df3f60e1ad8
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>