Cherry-pick FlatpakReference constructor from master branch for use in tests
It would be faster and less error-prone if we didn't have to adjust testing code between master and Plasma/5.27 when most of the parameters were shuffled and/or renamed.
It would be faster and less error-prone if we didn't have to adjust testing code between master and Plasma/5.27 when most of the parameters were shuffled and/or renamed.