cleanup tests [qtbase]: usages of QTest::qWait(int ms)

This API (unconditional wait) enables people to write bad and flakey tests. Should this API be eventually deprecated? Maybe there are valid use cases for it? Need to look at the test first. Maybe some other primitives should be build on top of https://codereview.qt-project.org/#/c/205012/ instead?

Counting with grep in qtbase at 40fe5d43fdc6a95332d19de3e716aab5040dee19 :

qtbase/tests/auto$ grep -r "QTest::qWait(" * | wc -l
1118 <------- !!!!!