Disable keyboard controller input while swkbd is open (foreground) (second attempt) (#6808)

* Block input updates while swkbd is open in foreground mode

* Flush internal driver state before unblocking input updates

* Rename Flush to Clear and remove unnecessary attribute

* Clear the driver state only if the GamepadDriver isn't null

src/Ryujinx.Gtk3/Input/GTK3/GTK3KeyboardDriver.cs

@@ -81,6 +81,11 @@ namespace Ryujinx.Input.GTK3
             return _pressedKeys.Contains(nativeKey);
         }
 
+        public void Clear()
+        {
+            _pressedKeys.Clear();
+        }
+
         public IGamepad GetGamepad(string id)
         {
             if (!_keyboardIdentifers[0].Equals(id))