Make Viewport input events fully Qt based (#2142)

* Make Viewport input events fully Qt based.

This should fix an issue with Qt touch event -> mouse event translation in the Editor, and may also fix issues with the Mac Editor and remote desktop (though, lacking the requisite hardware, I can test precisely none of these things personally).

See https://github.com/o3de/o3de/issues/1889

- Adapted LegacyViewportCameraController to use Movement::X & Y (mostly for testing purposes, it's on the slate for being removed soon)
- Moved cursor capture logic from RenderViewportWidget into QtEventToAzInputManager so that it can make sure it generates correct movement deltas
- Removed ViewportMouseCursorRequests::PreviousViewportCursorScreenPosition to have our viewport controllers use our dedicated Movement::X and Y channels instead, which will work in the launcher

Signed-off-by: nvsickle <nvsickle@amazon.com>

* Address review feedback

Signed-off-by: nvsickle <nvsickle@amazon.com>

* Fix Linux build

Signed-off-by: nvsickle <nvsickle@amazon.com>

Code/Editor/LegacyViewportCameraController.h

@@ -69,7 +69,7 @@ namespace SandboxEditor
 
         AZ::RPI::ViewportContextPtr GetViewportContext();
 
-        bool HandleMouseMove(const AzFramework::ScreenPoint& currentMousePos, const AzFramework::ScreenPoint& previousMousePos);
+        bool HandleMouseMove(int dx, int dy);
         bool HandleMouseWheel(float zDelta);
         bool IsKeyDown(Qt::Key key) const;
         void UpdateCursorCapture(bool shouldCaptureCursor);