Set actualWindowState earlier.

Previously, `_actualWindowState` was being set after the window state had finished changing, but `ExitFullScreenMode` calls `UpdateStyle` which expects `_actualWindowState` to be up-to-date, meaning that previously we ended up with an invalid size when exiting full screen mode programatically.

native/Avalonia.Native/src/OSX/WindowImpl.mm

@@ -488,6 +488,8 @@ HRESULT WindowImpl::SetWindowState(AvnWindowState state) {
         }
 
         if (_shown) {
+            _actualWindowState = _lastWindowState;
+
             switch (state) {
                 case Maximized:
                     if (currentState == FullScreen) {
@@ -545,7 +547,6 @@ HRESULT WindowImpl::SetWindowState(AvnWindowState state) {
                     break;
             }
 
-            _actualWindowState = _lastWindowState;
             WindowEvents->WindowStateChanged(_actualWindowState);
         }