QTestLlib: Stop using QCursor:pos() for mouse event geometry

QMouseEvent has a constructor which takes a single local position and then sets the global position by calling QCursor::pos(). This constructor is used several places in our unit tests, often in conjunction with a QCursor::setPos() call or a QTest::mouseEvent () call (see below).

On macOS 10.14+, QCursor::setPos() requires user approval (via system dialog interaction), and is no longer suitable for auto test use.

Existing QTestLib API:
(qtestmouse.h)

• QTest::mouseEvent(MouseAction, QWindow *, LocalPosition, …)
  Creates and sends a mouse event (correctly), using window->mapToGlobal() to get global coordinates.
• QTest::mouseEvent(MouseAction, QWidget *, LocalPosition, …)
  As the QWindow version, except that it has an exception for MouseMove events: in this case (only), QCursor::setPos() is called, and no mouse event is created or sent.

Fixes:

• Manually patch tests code which creates QMouseEvents, starting with the ones that fail on macOS 10,14:
  https://codereview.qt-project.org/c/qt/qtbase/+/264434

• Change QTest::mouseEvent() to send a mouse event in all cases, and port tests to use that.
  OR
• Introduce new API for creating mouse events: QTest::createMouseEvent()

Change history:

• d130382776e8b9db491385a0db45a3daaa79890c added QWindow overload for mouseEvent()
• 1762bf3394219db3a7a9cc99306f4111e6cb8492 replaced the QCursor::setPos() call with QWindowSystemInterface::handleMouseEvent(), for the QWindow overload.