Add batch_keyframe_idx on ControlNetUnit (#2926)

batch_keyframe_idx is needed by AnimateDiff for SparseCtrl

internal_controlnet/args.py

@@ -228,6 +228,7 @@ def parse_ipadapter_input(cls, value) -> Optional[List[torch.Tensor]]:
     animatediff_batch: bool = False
     batch_modifiers: list = []
     batch_image_files: list = []
+    batch_keyframe_idx: Optional[str|list] = None
 
     @property
     def accepts_multiple_inputs(self) -> bool: