gamemode: refactor pid passing to thread
gamemode: refactor pid passing to thread

Instead of having a pid and requester field, maintain an array,
which then can be more easily be worked with inside the target,
i.e. handle_call_thread.

flatpak/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,flatpak/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,flatpak/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,matthiasclasen/xdg-desktop-portal,flatpak/xdg-desktop-portal