Let -readconfig support parsing command line options into QDict or
QemuOpts.  This will be used to add back support for objects in
-readconfig.

Cc: Markus Armbruster <armbru@redhat.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210524105752.3318299-3-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>