Create unit test (generation tool) for use of QtConcurrent with move-only sequences and items

This is about the filter and map functions in QtConcurrent. They accept a sequence of items and some of them return a sequence of items.

Unit tests should be created which test:

1. Using move-only sequences as input
2. Using sequences of move-only items as input
3. Using move-only sequences as output
4. Using sequences of move-only items as output

With the current code, (1) should work. (2), (3), and (4) are known to not work.

The goal of this task is to have four patches in Gerrit of which one (1) is merged, the others waiting for improvements in QtConcurrent to be merged thereafter.

While this task talks about move-only types, the underlying motivation is to make sure the code moves when there are moveable objects (rvalues, temporaries). It's just easier to test whether the code works on move-only types than to test whether the code moves moveable objects.