[Refactor] Consolidate SupportsEagle (#36063)

Signed-off-by: Benjamin Chislett <bchislett@nvidia.com>

vllm/model_executor/models/llama.py

@@ -61,6 +61,7 @@ from vllm.v1.attention.backend import AttentionType
 
 from .adapters import as_embedding_model, as_seq_cls_model
 from .interfaces import (
+    EagleModelMixin,
     SupportsEagle,
     SupportsEagle3,
     SupportsLoRA,
@@ -351,7 +352,7 @@ def llama_model_invariants(
     # mark_unbacked_dims={"input_ids": 0},
     shape_invariants=llama_model_invariants
 )
-class LlamaModel(nn.Module):
+class LlamaModel(nn.Module, EagleModelMixin):
     def __init__(
         self,
         *,
@@ -389,8 +390,6 @@ class LlamaModel(nn.Module):
         else:
             self.norm = PPMissingLayer()
 
-        self.aux_hidden_state_layers = tuple[int, ...]()
-
         self.make_empty_intermediate_tensors = make_empty_intermediate_tensors_factory(
             ["hidden_states", "residual"], config.hidden_size
         )
@@ -417,15 +416,16 @@ class LlamaModel(nn.Module):
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
 
-        aux_hidden_states = []
+        aux_hidden_states = self._maybe_add_hidden_state([], 0, hidden_states, residual)
         for idx, layer in enumerate(
             islice(self.layers, self.start_layer, self.end_layer)
         ):
-            if idx in self.aux_hidden_state_layers:
-                aux_hidden_states.append(hidden_states + residual)
             hidden_states, residual = layer(
                 positions, hidden_states, residual, **extra_layer_kwargs
             )
+            self._maybe_add_hidden_state(
+                aux_hidden_states, idx + 1, hidden_states, residual
+            )
 
         if not get_pp_group().is_last_rank:
             return IntermediateTensors(
@@ -556,18 +556,6 @@ class LlamaForCausalLM(
             self.model.make_empty_intermediate_tensors
         )
 
-    def set_aux_hidden_state_layers(self, layers: tuple[int, ...]) -> None:
-        self.model.aux_hidden_state_layers = layers
-
-    def get_eagle3_aux_hidden_state_layers(self) -> tuple[int, ...]:
-        """Override to return default layers for Llama
-
-        Note: The GPU model runner will override this with layers from
-        the speculative config if available, providing dynamic configuration.
-        """
-        num_layers = len(self.model.layers)
-        return (2, num_layers // 2, num_layers - 3)
-
     def _init_model(
         self,
         vllm_config: VllmConfig,