Change LockingType to use DelegateClass

Significantly faster than `SimpleDelegator`.

activerecord/lib/active_record/locking/optimistic.rb

@@ -184,7 +184,7 @@ module ActiveRecord
       end
     end
 
-    class LockingType < SimpleDelegator # :nodoc:
+    class LockingType < DelegateClass(Type::Value) # :nodoc:
       def type_cast_from_database(value)
         # `nil` *should* be changed to 0
         super.to_i