xdg: sync pending when applying geometry

xdg: sync pending when applying geometry

Applications may respond to pending resize requests either by ignoring
them or substituting alternative sizes (for example, when mpv constrains
resizes to keep its aspect ratio fixed). In these cases, view->pending
will fall out of sync with the actual view geometry. This will cause
problems when subsequent operations (e.g., MoveToEdge) use the pending
geometry to decide where to place the window.

To fix this, reset view->pending to be equal view->current when either:

1. The requested size change has been commited, to the scene graph, and
   no subsequent changes are pending; or

2. The requested size change has been ignored by the client.