Model + API: GPU split updates and fixes

For the TP loader, GPU split cannot be an empty array. However,
defaulting the parameter to an empty array makes it easier to calculate
the device list. Therefore, cast an empty array to None using
falsy comparisons at load time.

Also add draft_gpu_split to the load request.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

endpoints/core/types/model.py

@@ -63,7 +63,10 @@ class DraftModelLoadRequest(BaseModel):
         default=None,
         examples=[1.0],
     )
-    draft_cache_mode: Optional[str] = None
+    draft_gpu_split: Optional[List[float]] = Field(
+        default_factory=list,
+        examples=[[24.0, 20.0]],
+    )
 
 
 class ModelLoadRequest(BaseModel):
@@ -94,7 +97,7 @@ class ModelLoadRequest(BaseModel):
     gpu_split_auto: Optional[bool] = None
     autosplit_reserve: Optional[List[float]] = None
     gpu_split: Optional[List[float]] = Field(
-        default=None,
+        default_factory=list,
         examples=[[24.0, 20.0]],
     )
     rope_scale: Optional[float] = Field(