Bugfix group order (#3323)

* Add ordered dict config validator

* Have group component use ordered dict config validator

* Improve config_validation testing

* update doc string config_validation.ordered_dict

* validate full dict entries

* Further simplify ordered_dict validator.

* Lint fix

homeassistant/helpers/config_validation.py

@@ -1,4 +1,5 @@
 """Helpers for config validation using voluptuous."""
+from collections import OrderedDict
 from datetime import timedelta
 import os
 from urllib.parse import urlparse
@@ -290,6 +291,27 @@ def url(value: Any) -> str:
     raise vol.Invalid('invalid url')
 
 
+def ordered_dict(value_validator, key_validator=match_all):
+    """Validate an ordered dict validator that maintains ordering.
+
+    value_validator will be applied to each value of the dictionary.
+    key_validator (optional) will be applied to each key of the dictionary.
+    """
+    item_validator = vol.Schema({key_validator: value_validator})
+
+    def validator(value):
+        """Validate ordered dict."""
+        config = OrderedDict()
+
+        for key, val in value.items():
+            v_res = item_validator({key: val})
+            config.update(v_res)
+
+        return config
+
+    return validator
+
+
 # Validator helpers
 
 def key_dependency(key, dependency):