screen-cast: Pass remote desktop session on construction

We already have the remote desktop session ID, and we'll soon need the
actual remote desktop session in the screen cast session, so pass it on
construction.

The old screen cast type is set implicitly instead.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3228>

src/backends/meta-backend-types.h

@@ -62,6 +62,7 @@ typedef struct _MetaRenderer MetaRenderer;
 typedef struct _MetaRendererView MetaRendererView;
 
 typedef struct _MetaRemoteDesktop MetaRemoteDesktop;
+typedef struct _MetaRemoteDesktopSession MetaRemoteDesktopSession;
 typedef struct _MetaScreenCast MetaScreenCast;
 typedef struct _MetaScreenCastSession MetaScreenCastSession;
 typedef struct _MetaScreenCastStream MetaScreenCastStream;