Dev 3.x flat package (#961)

* Move packages

* Added changelog

* Update examples/echo_bot.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

* Rename `handler` -> `handlers`

* Update __init__.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

tests/test_fsm/storage/test_isolation.py

@@ -0,0 +1,30 @@
+import pytest
+
+from aiogram.fsm.storage.base import BaseEventIsolation, StorageKey
+from tests.mocked_bot import MockedBot
+
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.fixture(name="storage_key")
+def create_storate_key(bot: MockedBot):
+    return StorageKey(chat_id=-42, user_id=42, bot_id=bot.id)
+
+
+@pytest.mark.parametrize(
+    "isolation",
+    [
+        pytest.lazy_fixture("redis_isolation"),
+        pytest.lazy_fixture("lock_isolation"),
+        pytest.lazy_fixture("disabled_isolation"),
+    ],
+)
+class TestIsolations:
+    async def test_lock(
+        self,
+        bot: MockedBot,
+        isolation: BaseEventIsolation,
+        storage_key: StorageKey,
+    ):
+        async with isolation.lock(bot=bot, key=storage_key):
+            assert True, "You are kidding me?"