[wayland] Sync resizes

Similar to X11 world: we send a sync request on each size change and
block till we get the next damage with the proper size.

Testing seems to show a very smooth resize experience. We automatically
sync to the resize speed of the client.

Maybe we need a timeout in case the client isn't able to resize to the
requested size.

shell_client.cpp

@@ -739,4 +739,14 @@ QPoint ShellClient::transientPlacementHint() const
     return m_shellSurface->transientOffset();
 }
 
+bool ShellClient::isWaitingForMoveResizeSync() const
+{
+    return m_positionAfterResize.isValid();
+}
+
+void ShellClient::doResizeSync()
+{
+    requestGeometry(moveResizeGeometry());
+}
+
 }

shell_client.h

@@ -122,6 +122,8 @@ protected:
     void setGeometryRestore(const QRect &geo) override {
         m_geomMaximizeRestore = geo;
     }
+    void doResizeSync() override;
+    bool isWaitingForMoveResizeSync() const override;
 
 private Q_SLOTS:
     void clientFullScreenChanged(bool fullScreen);

utils.h

@@ -206,7 +206,7 @@ static inline int bitCount(uint32_t mask)
 class ClearablePoint
 {
 public:
-    inline bool isValid() {
+    inline bool isValid() const {
         return m_valid;
     }