[Spec Decode] Introduce DraftModelRunner (#5799)

tests/spec_decode/utils.py

@@ -14,6 +14,7 @@ from vllm.sequence import (CompletionSequenceGroupOutput, Logprob,
                            SequenceOutput)
 from vllm.utils import get_distributed_init_method, get_ip, get_open_port
 from vllm.worker.cache_engine import CacheEngine
+from vllm.worker.model_runner import ModelRunner
 from vllm.worker.worker import Worker
 
 T = TypeVar("T", bound=Worker)
@@ -66,7 +67,8 @@ def create_worker(cls: Callable[..., T],
                   num_gpu_blocks: int,
                   seed: int,
                   is_driver_worker: bool = True,
-                  enforce_eager: bool = True) -> T:
+                  enforce_eager: bool = True,
+                  model_runner_cls: Optional[ModelRunner] = None) -> T:
     engine_args = EngineArgs(
         model=model_name,
         seed=seed,
@@ -89,6 +91,7 @@ def create_worker(cls: Callable[..., T],
         rank=0,
         distributed_init_method=distributed_init_method,
         is_driver_worker=is_driver_worker,
+        model_runner_cls=model_runner_cls,
     )
 
     worker.init_device()