Fix circular imports caused by type annotations

Imports that are only necessary for type annotations should be guarded.

src/zino/flaps.py

@@ -3,6 +3,8 @@
 Flapping is normally only tracked/updated based on incoming link traps.
 """
 
+from __future__ import annotations
+
 import logging
 from datetime import datetime
 from typing import TYPE_CHECKING, List, Optional, Tuple

src/zino/tasks/task.py

@@ -1,8 +1,14 @@
+from __future__ import annotations
+
 from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
 
 from zino.config.models import PollDevice
 from zino.snmp import SNMP
-from zino.state import ZinoState
+
+if TYPE_CHECKING:
+    from zino.state import ZinoState
+
 from zino.statemodels import DeviceState