Implement action feature (#849)

Adds `FeatureType.Action` making it possible to expose features like
"reboot", "test alarm", "pair" etc.

The `attribute_getter` is no longer mandatory, but it will raise an
exception if not defined for other types than actions.
Trying to read returns a static string `<Action>`.
This overloads the `set_value` to call the given callable on any value.

This also fixes the `play` and `stop` coroutines of the alarm module to
await the call.

kasa/tests/test_feature.py

@@ -3,11 +3,13 @@ import pytest
 from kasa import Feature, FeatureType
 
 
+class DummyDevice:
+    pass
+
+
 @pytest.fixture
 def dummy_feature() -> Feature:
     # create_autospec for device slows tests way too much, so we use a dummy here
-    class DummyDevice:
-        pass
 
     feat = Feature(
         device=DummyDevice(),  # type: ignore[arg-type]
@@ -79,3 +81,19 @@ async def test_feature_setter_read_only(dummy_feature):
     dummy_feature.attribute_setter = None
     with pytest.raises(ValueError):
         await dummy_feature.set_value("value for read only feature")
+
+
+async def test_feature_action(mocker):
+    """Test that setting value on button calls the setter."""
+    feat = Feature(
+        device=DummyDevice(),  # type: ignore[arg-type]
+        name="dummy_feature",
+        attribute_setter="call_action",
+        container=None,
+        icon="mdi:dummy",
+        type=FeatureType.Action,
+    )
+    mock_call_action = mocker.patch.object(feat.device, "call_action", create=True)
+    assert feat.value == "<Action>"
+    await feat.set_value(1234)
+    mock_call_action.assert_called()