DEV: Validate objects when updating typed objects theme settings (#25902)

Why this change?

This change ensures that we validate the value of the new objects
when updating typed objects theme settings.

lib/theme_settings_manager/objects.rb

@@ -6,7 +6,7 @@ class ThemeSettingsManager::Objects < ThemeSettingsManager
   end
 
   def value=(objects)
-    # TODO: Validate the objects against the schema
+    ensure_is_valid_value!(objects)
 
     record = has_record? ? db_record : create_record!
     record.json_value = objects

lib/theme_settings_object_validator.rb

@@ -61,7 +61,7 @@ class ThemeSettingsObjectValidator
   end
 
   def initialize(schema:, object:, json_pointer_prefix: "", errors: {}, valid_ids_lookup: {})
-    @object = object
+    @object = object.with_indifferent_access
     @schema_name = schema[:name]
     @properties = schema[:properties]
     @errors = errors