Adds the \Stringable interface to classes that have __toString() method (#5920)

Co-authored-by: 李铭昕 <[email protected]>

Author: huangdijia

src/Definition/DefinitionInterface.php

@@ -11,7 +11,9 @@
  */
 namespace Hyperf\Di\Definition;
 
-interface DefinitionInterface
+use Stringable;
+
+interface DefinitionInterface extends Stringable
 {
     /**
      * Definitions can be cast to string for debugging information.