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/Framework/AzToolsFramework/AzToolsFramework/Viewport/ViewportMessages.h

@@ -276,11 +276,6 @@ namespace AzToolsFramework
             virtual void EndCursorCapture() = 0;
             //! Gets the most recent recorded cursor position in the viewport in screen space coordinates.
             virtual AzFramework::ScreenPoint ViewportCursorScreenPosition() = 0;
-            //! Gets the cursor position recorded prior to the most recent cursor position.
-            //! Note: The cursor may be captured by the viewport, in which case this may not correspond to the last result
-            //! from ViewportCursorScreenPosition. This method will always return the correct position to generate a mouse
-            //! position delta.
-            virtual AZStd::optional<AzFramework::ScreenPoint> PreviousViewportCursorScreenPosition() = 0;
             //! Is mouse over viewport.
             virtual bool IsMouseOver() const = 0;