floating: Add proper recalculate function

Don't just check maximized windows on every refresh, remapping them and
causing flickering, but introduce a proper recalculate method to be
called on layer-shell events / set_output event.

Also if we need to remap, remap all windows to keep stacking order.

src/shell/workspace.rs

@@ -491,7 +491,7 @@ impl Workspace {
 
     pub fn recalculate(&mut self) {
         self.tiling_layer.recalculate();
-        self.floating_layer.refresh();
+        self.floating_layer.recalculate();
     }
 
     pub fn unmaximize_request(&mut self, elem: &CosmicMapped) -> Option<Size<i32, Logical>> {