Register imemo_ment as a pinning object

It sometimes pins itself when it is in the overloaded_cme table.

Author: peterzhu2118

vm_method.c

@@ -1119,6 +1119,10 @@ rb_method_entry_alloc(ID called_id, VALUE owner, VALUE defined_class, rb_method_
         VM_ASSERT_TYPE2(defined_class, T_CLASS, T_ICLASS);
     }
     rb_method_entry_t *me = SHAREABLE_IMEMO_NEW(rb_method_entry_t, imemo_ment, defined_class);
+
+    // mark_and_move_method_entry pins itself when it is in the overloaded_cme table
+    rb_gc_register_pinning_obj((VALUE)me);
+
     *((rb_method_definition_t **)&me->def) = def;
     me->called_id = called_id;
     me->owner = owner;