Camera compatibility issues due to removal of DirectShow

The removal of the DirectShow backend in Qt6 caused a bunch of 3rdparty drivers and software to be incompatible with the Qt multimedia camera module.

Examples of this are OBS or the PS-Eye driver.

Users were able to use these as camera with Qt5, but now in Qt6 they simply don't show up in the QMediaDevices::videoInputs() list.

While I'm sure that it's a good thing to remove deprecated backends in the long run, I don't think it was a wise decision to do it while it's still a common choice for 3rdparty software in the current Windows version.