`ewmhFullscreen` doesn't restore floating windows

[geekosaur]

If a floating window is made fullscreen and then toggled back, it is sunk instead of floated. The code at https://github.com/xmonad/xmonad-contrib/blob/afd6824ce00063bb8e9b7a1c5daf0737c2f61616/XMonad/Hooks/EwmhDesktops.hs#L442C5-L444 unconditionally sinks the window when _NET_WM_STATE_FULLSCREEN is removed.

This will require saving the old window position for floats; the current code assumes sinking the window will handle positioning.

Checklist

• [x] I've read CONTRIBUTING.md

• I tested my configuration

  • [x] With xmonad version 0.17.2
  • [x] With xmonad-contrib version 0.17.1

[geekosaur]

This could reasonably be parked until it matters to someone. Also, it's better not to try to address it until #866 goes in, since otherwise there will be a merge conflict.

[liskin]

I believe https://github.com/xmonad/xmonad-contrib/pull/768 solved this already.

[geekosaur]

"This commit only adds the hooks. Neither of the motivations are dealt with yet, so the docs are a bit terse still."

[liskin]

Well that's the first commit. The following one adds the thing.