(Partly) fix handling of client-initiated configure requests

(Partly) fix handling of client-initiated configure requests

- Add missing call to wlr_scene_node_set_position() in
  unmanaged_handle_commit() -- this fixes moving unmanaged XWayland
  windows.

- Update view->pending_move_resize when we receive a configure request
  for a managed XWayland surface -- this fixes moving managed but
  undecorated XWayland windows.

- Also update view->pending_move_resize when we move a surface while a
  configure request is already pending -- this fixes a discrepancy
  between displayed and actual position for XWayland windows that try to
  set their own initial position, but then get overridden by labwc's
  positioning.

Moving undecorated XWayland windows is still really glitchy -- it appears
that an XWayland window gets sent incorrect mouse motion coordinates when
there is a pending configure request moving the window itself.