Check the wlr_layer_surface_v1_state.committed bitmask to see if we need to rearrange. This is also what sway does.

Without this check, every commit request (even if only the attached buffer changed) will lead to another configure event, which will lead to another commit, etc.

This loop results in swaybg consuming 100% CPU.

Co-authored-by: Owen Rafferty <owen@owenrafferty.com>