More core reorganization

swh/provenance/algos/__init__.py

swh/provenance/algos/directory.py

swh/provenance/algos/isochrone_graph.py

swh/provenance/algos/origin.py

swh/provenance/algos/revision.py

swh/provenance/cli.py

swh/provenance/journal_client.py

swh/provenance/tests/test_consistency.py

swh/provenance/tests/test_directory_flatten.py

swh/provenance/tests/test_directory_iterator.py

swh/provenance/tests/test_history_graph.py

swh/provenance/tests/test_isochrone_graph.py

swh/provenance/tests/test_origin_iterator.py

swh/provenance/tests/test_origin_revision_layer.py

swh/provenance/tests/test_provenance_storage.py

swh/provenance/tests/test_revision_content_layer.py

swh/provenance/tests/test_revision_iterator.py