ui: Move HMP commands from monitor to new ui/ui-hmp-cmds.c

This moves these commands from MAINTAINERS section "Human
Monitor (HMP)" to "Graphics".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230109190321.1056914-12-armbru@redhat.com>