feat: support --fake for aerich upgrade (#398)

* feat: support `--fake` for aerich upgrade

* Add `--fake` to downgrade

* tests: check --fake result for aerich upgrade and downgrade

* Update readme

* Fix unittest failed because of `db_field_types` changed

* refactor: improve type hints and document

tests/assets/sqlite_migrate/conftest_.py

@@ -0,0 +1,26 @@
+import asyncio
+from typing import Generator
+
+import pytest
+import pytest_asyncio
+import settings
+from tortoise import Tortoise, connections
+
+
+@pytest.fixture(scope="session")
+def event_loop() -> Generator:
+    policy = asyncio.get_event_loop_policy()
+    res = policy.new_event_loop()
+    asyncio.set_event_loop(res)
+    res._close = res.close  # type:ignore[attr-defined]
+    res.close = lambda: None  # type:ignore[method-assign]
+
+    yield res
+
+    res._close()  # type:ignore[attr-defined]
+
+
+@pytest_asyncio.fixture(scope="session", autouse=True)
+async def api(event_loop, request):
+    await Tortoise.init(config=settings.TORTOISE_ORM)
+    request.addfinalizer(lambda: event_loop.run_until_complete(connections.close_all(discard=True)))