Enably QtForPython for Linux (#5667)

- Fix PALification and include Linux for the QtForPython gem
- Add Linux-only module loader for Pyside2 related modules
- Remove (unnecessary) #if !defined(Q_OS_WIN)

Signed-off-by: Steve Pham <82231385+spham-amzn@users.noreply.github.com>

Gems/QtForPython/Code/Source/Platform/Windows/InitializeEmbeddedPyside2.h

@@ -0,0 +1,18 @@
+/*
+ * 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
+
+namespace QtForPython
+{
+    class InitializeEmbeddedPyside2
+    {
+    public:
+        InitializeEmbeddedPyside2() = default;
+        virtual ~InitializeEmbeddedPyside2() = default;
+    };
+} // namespace QtForPython