Improve supported module checks for hub children (#1188)

No devices in `fixtures/smart/child` support the `get_device_time` or
`get_device_usage` methods so this PR tests for whether the device is a
hub child and marks those modules/methods as not supported. This
prevents features being erroneously created on child devices.

It also moves the logic for getting the time from the parent module
behind getting it from the child module which was masking the creation
of these unsupported modules.

kasa/tests/test_childdevice.py

@@ -1,7 +1,9 @@
 import inspect
 import sys
+from datetime import datetime, timezone
 
 import pytest
+from freezegun.api import FrozenDateTimeFactory
 
 from kasa import Device
 from kasa.device_type import DeviceType
@@ -120,3 +122,15 @@ async def test_parent_property(dev: Device):
     assert dev.parent is None
     for child in dev.children:
         assert child.parent == dev
+
+
+@has_children_smart
+async def test_child_time(dev: Device, freezer: FrozenDateTimeFactory):
+    """Test a child device gets the time from it's parent module."""
+    if not dev.children:
+        pytest.skip(f"Device {dev} fixture does not have any children")
+
+    fallback_time = datetime.now(timezone.utc).astimezone().replace(microsecond=0)
+    assert dev.parent is None
+    for child in dev.children:
+        assert child.time != fallback_time