feat: propagate client window metadata

[FreddyFunk]

Use X11 _NET_WM_ICON and native Wayland xdg-toplevel-icon-v1 metadata. Publish bounded icons and PIDs over COSMIC toplevel-info v4 so cosmic-applets can use them to properly show icons and and application names in dock.

depends on Smithay/smithay#2160
depends on pop-os/cosmic-protocols#87

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