Add first set of functional tests

• Mock storage and dev server
• Dummy storage data
• Functional tests for OriginNode and OriginConnection

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Migrated from D7817 (view on Phabricator)

swh/graphql/resolvers/origin.py

+# Copyright (C) 2022 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
 from swh.graphql.backends import archive
 
 from .base_connection import BaseConnection