Add support for screen casting, using pipewire for creating streams. Screen data
is supplied by KWin which sends us GBM fd using Remote Access interface from KWayland.
Note that this is meant for sandboxed and also not sandboxed applications as plan for Pipewire is that
if application talks directly to Pipewire, not calling xdg-desktop-portal (the middle man), then Pipewire
will still call backend implementation internally, in our case xdg-desktop-portal-kde to get screen cast stream.