adding missing includes to fix build

Signed-off-by: Guthrie Adams <guthadam@amazon.com>

Gems/Atom/Tools/AtomToolsFramework/Code/Include/AtomToolsFramework/PreviewRenderer/PreviewContent.h

@@ -9,6 +9,7 @@
 #pragma once
 
 #include <AzCore/Memory/Memory.h>
+#include <AzCore/Memory/SystemAllocator.h>
 
 namespace AtomToolsFramework
 {

Gems/Atom/Tools/AtomToolsFramework/Code/Include/AtomToolsFramework/PreviewRenderer/PreviewRendererCaptureRequest.h

@@ -10,6 +10,9 @@
 
 #include <AtomToolsFramework/PreviewRenderer/PreviewContent.h>
 #include <AzCore/Memory/Memory.h>
+#include <AzCore/Memory/SystemAllocator.h>
+#include <AzCore/std/functional.h>
+#include <AzCore/std/smart_ptr/shared_ptr.h>
 
 class QPixmap;