Mark tst_qquicktrailsemitter insignificant on windows

Has been blocking CI intermittently, but not locally reproducable.

Task-number: QTBUG-33421
Change-Id: I0e876fe1f236a00a9ecad2231aa7ff50a4b8d590
Reviewed-by: Simo Fält <simo.falt@digia.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Fix qmlClearTypeRegistrations tests

The manual test now tests that QtQuick can be loaded second try, and an
autotest has been added to ensure that the function does not affect
correctness.

Task-Number: QTBUG-32078
Change-Id: Ifd55e12c2c31e2e181054f897f10f02a2811c5d1
Reviewed-by: Christopher Adams <chris.adams@jollamobile.com>