QCamera should support multi-camera configs on Android

Our FFmpeg backend on Android does not currently support using multi-cameras on Android. Multi-camera configurations means phones that, for example, have multiple cameras on the back side that have different camera lenses. Such as a phone that has a wide-lens, normal lens and high-zoom lens.

One issue with this approach is that our backend seems to report incorrect zoom-ranges, meaning that in some cases a camera can report a minimumZoomFactor() as less than 1, while the zoom does nothing when you set it to less than 1.

This also has an impact on how viable Qt appears as a viable framework for mobile development, since we cannot provide the same camera experience as other frameworks can. Ideally we would present functionality where the developer can easily zoom through cameras and have it automatically change lenses, which gives you much better image quality than a digital zoom.

This should be possible to implement without any updates to the public API. My suggestion is that we update the public documentation to mention that these multi-camera configs are chosen under-the-hood and will change the physical camera lens automatically during zoom. Additionally, we might introduce some information on which zoomFactors this change happens, so the user can "snap" their zoom into the ideal zoomFactor for maximum image quality. Either way this change will require some refactoring on the Android FFmpeg backend.

See more info here for the relevant API:
https://developer.android.com/media/camera/camera2/multi-camera