support speculative execution for openai API (#48)

Co-authored-by: Ying Sheng <sqy1415@gmail.com>

test/srt/test_fast_forward.py

@@ -1,7 +1,6 @@
 import argparse
 from enum import Enum
 
-import sglang as sgl
 from pydantic import BaseModel, constr
 from sglang.srt.constrained.json_schema import build_regex_from_object
 from sglang.test.test_utils import (
@@ -9,6 +8,8 @@ from sglang.test.test_utils import (
     select_sglang_backend,
 )
 
+import sglang as sgl
+
 IP_REGEX = r"((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)"
 
 ip_fast_forward = (