Expose camera input channels to the UI and ensure the cached values are refreshed when updated (#3607)

* expose camera input channels to the ui and ensure the cached values are refreshed when updated

Signed-off-by: hultonha <hultonha@amazon.co.uk>

* small fixes for tests

Signed-off-by: hultonha <hultonha@amazon.co.uk>

Code/Editor/EditorModularViewportCameraComposerBus.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzCore/EBus/EBus.h>
+#include <AzFramework/Viewport/ViewportId.h>
+#include <AzToolsFramework/Viewport/ViewportMessages.h>
+
+namespace SandboxEditor
+{
+    //! Notifications for changes to the editor modular viewport camera controller.
+    class EditorModularViewportCameraComposerNotifications
+    {
+    public:
+        //! Notify any listeners when changes have been made to the modular viewport camera settings.
+        //! @note This is used to update any cached input channels when controls are modified.
+        virtual void OnEditorModularViewportCameraComposerSettingsChanged() = 0;
+
+    protected:
+        ~EditorModularViewportCameraComposerNotifications() = default;
+    };
+
+    using EditorModularViewportCameraComposerNotificationBus =
+        AZ::EBus<EditorModularViewportCameraComposerNotifications, AzToolsFramework::ViewportInteraction::ViewportEBusTraits>;
+} // namespace SandboxEditor