Fix the names of some files top reflect the renaming

src/_zkapauthorizer/__init__.py

src/_zkapauthorizer/_base64.py

src/_zkapauthorizer/_plugin.py

src/_zkapauthorizer/_storage_client.py

src/_zkapauthorizer/_storage_server.py

src/_zkapauthorizer/api.py

src/_zkapauthorizer/controller.py

src/_zkapauthorizer/model.py

src/_zkapauthorizer/newsfragments/.gitignore

src/_zkapauthorizer/resource.py

src/_zkapauthorizer/tests/__init__.py

src/_zkapauthorizer/tests/matchers.py

src/_zkapauthorizer/tests/strategies.py

src/_zkapauthorizer/tests/test_base64.py

src/_zkapauthorizer/tests/test_client_resource.py

src/_zkapauthorizer/tests/test_matchers.py

src/_zkapauthorizer/tests/test_model.py

src/_zkapauthorizer/tests/test_plugin.py

src/_zkapauthorizer/tests/test_storage_protocol.py

src/_zkapauthorizer/tests/test_strategies.py