Expose vsync interval with new cvar rpi_vsync_interval and support Vulkan vsync (#2061)

* Expose vsync interval with new cvar rpi_vsync_interval

On change, the rpi_vsync_interval is broadcasted to a new event on
the WindowNotificationBus and all swapchains are recreated with the
new vsync value.

Signed-off-by: Jeremy Ong <jeremycong@gmail.com>

* Add vsync interval support to the Vulkan RHI

Vsync intervals are not intrinsically supported using the Vulkan
swapchain extension. Instead, extra presents are enqueued for each
extra vblank requested past 1. Swapchain recreation is triggered
when transitioning to and from the FIFO presentation mode (when
rpi_vsync_interval transitions from and to 0 respectively).

Signed-off-by: Jeremy Ong <jeremycong@gmail.com>

* Rollback vsync > 1 implementation on Vulkan and leverage *Internal pattern

Signed-off-by: Jeremy Ong <jeremycong@gmail.com>

Code/Framework/AzFramework/AzFramework/Windowing/WindowBus.h

@@ -97,6 +97,9 @@ namespace AzFramework
 
         //! This is called when the window is deactivated from code or if the user closes the window.
         virtual void OnWindowClosed() {};
+
+        //! This is called when vsync interval is changed.
+        virtual void OnVsyncIntervalChanged(uint32_t interval) { AZ_UNUSED(interval); };
     };
     using WindowNotificationBus = AZ::EBus<WindowNotifications>;