scene surface-tree uses previous position for subsurfaces

Steps to reproduce:

• start tinywl with tinywl: use wlr_scene  #3250 (or another compositor using wlr_scene_subsurface_tree_create) and weston-subsurfaces
• if possible, toggle the window between floating and tiled/maximized several times, each time observe the result
• otherwise, quickly resize the window

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wlroots has migrated to gitlab.freedesktop.org. This issue has been moved to:

https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3316