Add iCloud discovery (#50304)

Since homekit requires iCloud keychains to be enabled, if they
have a homekit hub, they must have iCloud.

homeassistant/components/icloud/manifest.json

@@ -5,5 +5,6 @@
   "documentation": "https://www.home-assistant.io/integrations/icloud",
   "requirements": ["pyicloud==0.10.2"],
   "codeowners": ["@Quentame", "@nzapponi"],
+  "zeroconf": ["_homekit._tcp.local."],
   "iot_class": "cloud_polling"
 }

homeassistant/generated/zeroconf.py

@@ -91,6 +91,9 @@ ZEROCONF = {
     "_homekit._tcp.local.": [
         {
             "domain": "homekit"
+        },
+        {
+            "domain": "icloud"
         }
     ],
     "_http._tcp.local.": [