FA3 Spec Decoding to support top k = 1 and add cuda graph support (#5050)

Co-authored-by: Qingquan Song <ustcsqq@gmail.com>
Co-authored-by: Chunan Zeng <zcnrex@gmail.com>

python/sglang/srt/model_executor/forward_batch_info.py

@@ -104,6 +104,9 @@ class ForwardMode(IntEnum):
             or self == ForwardMode.IDLE
         )
 
+    def is_extend_or_draft_extend(self):
+        return self == ForwardMode.EXTEND or self == ForwardMode.DRAFT_EXTEND
+
     def is_dummy_first(self):
         return self == ForwardMode.DUMMY_FIRST