[V1][Spec Decode] Implement Eagle Proposer [1/N] (#15729)

Signed-off-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>

vllm/config.py

@@ -2152,9 +2152,10 @@ class SpeculativeConfig:
 
                 # Replace hf_config for EAGLE draft_model
                 if self.method == "eagle":
-                    if self.enable_chunked_prefill:
+                    if self.enable_chunked_prefill and not envs.VLLM_USE_V1:
                         raise ValueError(
-                            "Chunked prefill and EAGLE are not compatible.")
+                            "Chunked prefill and EAGLE are not compatible "
+                            "when using V0.")
 
                     from vllm.transformers_utils.configs.eagle import (
                         EAGLEConfig)