scripts: Add qom-cast-macro-clean-cocci-gen.py

Add a script to generate Coccinelle semantic patch
removing all pointless QOM cast macro uses.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230601093452.38972-2-philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>