Extend Auto Test Project wizard with optional setup code

Currently it only creates QUICK_TEST_MAIN, but there could be an option to generate QUICK_TEST_MAIN_WITH_SETUP with a class that already contains these 3 slots (hopefully including a comment about what they are about as in the table here):

https://doc.qt.io/qt-5/qtquicktest-index.html#executing-c-before-qml-tests