Fix RecursionError for (very) large graphs

[Acly]

ExecutionList adds nodes and links recursively. There are 3 recursive calls per node in a chain of nodes, which means you run into recursion limits at around 300 linked nodes (default recursion limit is 1000 in CPython).

  File "C:\Dev\ComfyUI\execution.py", line 492, in execute
    execution_list.add_node(node_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 125, in add_node
    self.add_strong_link(from_node_id, from_socket, unique_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 153, in add_strong_link
    super().add_strong_link(from_node_id, from_socket, to_node_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 102, in add_strong_link
    self.add_node(from_node_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 125, in add_node
    self.add_strong_link(from_node_id, from_socket, unique_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 153, in add_strong_link
    super().add_strong_link(from_node_id, from_socket, to_node_id)
  File "C:\Dev\ComfyUI\comfy_execution\graph.py", line 102, in add_strong_link
    self.add_node(from_node_id)
  [ ... repeats many times ...]
RecursionError: maximum recursion depth exceeded

This PR makes TopologicalSort.add_node add inputs in a while loop to avoid the problem.

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