Deprecate homekit_controller .homekit folder (#32158)

* homekit_controller: Deprecate .homekit folder

* Tweaks from review

* Delay it a release

homeassistant/components/homekit_controller/__init__.py

@@ -1,5 +1,6 @@
 """Support for Homekit device discovery."""
 import logging
+import os
 
 import aiohomekit
 from aiohomekit.model.characteristics import CharacteristicsTypes
@@ -227,6 +228,16 @@ async def async_setup(hass, config):
     hass.data[CONTROLLER] = aiohomekit.Controller()
     hass.data[KNOWN_DEVICES] = {}
 
+    dothomekit_dir = hass.config.path(".homekit")
+    if os.path.exists(dothomekit_dir):
+        _LOGGER.warning(
+            (
+                "Legacy homekit_controller state found in %s. Support for reading "
+                "the folder is deprecated and will be removed in 0.109.0."
+            ),
+            dothomekit_dir,
+        )
+
     return True