Include the QTest Protocol doc string in docs/devel/qtest.rst,
after converting it to use Sphinx syntax.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201005205228.697463-3-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>