[Refactor] Cuda Graph Runner/Backend Refactor (#23906)

Co-authored-by: BBuf <1182563586@qq.com>
Co-authored-by: Cheng Wan <54331508+ch-wan@users.noreply.github.com>
Co-authored-by: Lianmin Zheng <lianminzheng@gmail.com>

python/sglang/test/scripted_runtime/http_server.py

@@ -230,7 +230,7 @@ def _spawn_server_process(
         kv_canary="raise",
         kv_canary_real_data="partial",
         kv_canary_sweep_interval=100,
-        disable_piecewise_cuda_graph=True,
+        disable_prefill_cuda_graph=True,
     )
     launch_kwargs.update(engine_kwargs)
     http_port = launch_kwargs["port"]