Don't remove but deprecate DANGEROUS_CHANGE_IMPLEMENTED_INTERFACE_ADDED

Removing a public constant is a breaking change and can not be
implemented in a minor version. Instead the internal value is changed to
ensure that existing code keeps working with the new interface
implementation logic.

src/Utils/BreakingChangesFinder.php

@@ -53,6 +53,8 @@ class BreakingChangesFinder
     public const DANGEROUS_CHANGE_TYPE_ADDED_TO_UNION          = 'TYPE_ADDED_TO_UNION';
     public const DANGEROUS_CHANGE_OPTIONAL_INPUT_FIELD_ADDED   = 'OPTIONAL_INPUT_FIELD_ADDED';
     public const DANGEROUS_CHANGE_OPTIONAL_ARG_ADDED           = 'OPTIONAL_ARG_ADDED';
+    /** @deprecated use DANGEROUS_CHANGE_IMPLEMENTED_INTERFACE_ADDED instead, will be removed in v15.0.0. */
+    public const DANGEROUS_CHANGE_INTERFACE_ADDED_TO_OBJECT = 'IMPLEMENTED_INTERFACE_ADDED';
 
     /**
      * Given two schemas, returns an Array containing descriptions of all the types