Stabilize tst_qtouchevent.

- Use QTRY_COMPARE() in touchBeginWithGraphicsWidget.
- Change raw event translation tests to wait for the
  window to become active to avoid WM positioning issues.
- Blacklist the raw event translation tests on Linux.

Task-number: QTBUG-46266
Change-Id: I73aae375ee279a518a2a083d0ce8919cce474cb3
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>