feat: spec decode with draft models (#24322)

Signed-off-by: Tomas Ruiz <tomas.ruiz.te@gmail.com>

vllm/config/parallel.py

@@ -3,6 +3,7 @@
 
 import os
 from collections.abc import Callable
+from dataclasses import replace
 from typing import TYPE_CHECKING, Any, Literal
 
 import torch
@@ -709,3 +710,6 @@ class ParallelConfig:
             )
 
         return self
+
+    def replace(self, **kwargs) -> Self:
+        return replace(self, **kwargs)