Input facade: add cursor capture, mouse delta and scroll delta

SetCursorCaptured / IsCursorCaptured / GetMouseDelta / ConsumeScrollDelta
now route through the Input facade, so the editor camera no longer takes
a Window& at all: Camera::Update and EditorCamera::Update lose their
window parameter and SandboxApp calls Update(dt) directly. App layer
now has zero Window/GLFW usage for input - everything goes through
Engine::Input.

App/main.cpp

@@ -71,8 +71,7 @@ namespace
             if (GetRenderer().GetDisplayMode() == kDisplayViewport &&
                 !m_Editor->IsPlaying())
             {
-                GetRenderer().GetEditorCamera().Update(GetWindow(),
-                                                       frameTime.UnscaledDt());
+                GetRenderer().GetEditorCamera().Update(frameTime.UnscaledDt());
             }
         }