wrap the storage backend object directly rather than the Foolscap façade

src/_zkapauthorizer/_plugin.py

src/_zkapauthorizer/_storage_server.py

src/_zkapauthorizer/tests/fixtures.py

src/_zkapauthorizer/tests/foolscap.py

src/_zkapauthorizer/tests/storage_common.py

src/_zkapauthorizer/tests/test_storage_protocol.py

src/_zkapauthorizer/tests/test_storage_server.py