[V1][Usage] Refactor speculative decoding configuration and tests (#14434)

Signed-off-by: Shangming Cai <caishangming@linux.alibaba.com>

tests/spec_decode/e2e/test_integration_dist_tp4.py

@@ -24,12 +24,7 @@ SPEC_MODEL = "JackFram/llama-68m"
         "4",
     ]])
 @pytest.mark.parametrize("per_test_common_llm_kwargs", [
-    [
-        "--speculative-model",
-        f"{SPEC_MODEL}",
-        "--num-speculative-tokens",
-        "5",
-    ],
+    [],
 ])
 @pytest.mark.parametrize("baseline_llm_kwargs", [[]])
 @pytest.mark.parametrize(
@@ -37,8 +32,12 @@ SPEC_MODEL = "JackFram/llama-68m"
     [
         #TODO(wooyeon): add spec_draft_dp=2 case
         [
-            "--speculative-draft-tensor-parallel-size",
-            "1",
+            "--speculative_config",
+            str({
+                "model": f"{SPEC_MODEL}",
+                "num_speculative_tokens": 5,
+                "draft_tensor_parallel_size": 1,
+            }),
         ],
     ])
 @pytest.mark.parametrize("batch_size", [2])
@@ -78,15 +77,14 @@ def test_draft_model_tp_lt_target_model_tp4(common_llm_kwargs,
     "test_llm_kwargs",
     [
         [
-            "--speculative-model",
-            f"{SPEC_MODEL}",
-            "--num-speculative-tokens",
-            "5",
-
             # Artificially limit the draft model max model len; this forces vLLM
             # to skip speculation once the sequences grow beyond 32-k tokens.
-            "--speculative-max-model-len",
-            "32",
+            "--speculative_config",
+            str({
+                "model": f"{SPEC_MODEL}",
+                "num_speculative_tokens": 5,
+                "max_model_len": 32,
+            }),
         ],
     ])
 @pytest.mark.parametrize("batch_size", [8])