add networkx.topological_generations (#11927)

Author: rmorshea

stubs/networkx/networkx/algorithms/dag.pyi

@@ -11,6 +11,8 @@ def ancestors(G: Graph[_Node], source: _Node) -> set[_Node]: ...
 @_dispatch
 def is_directed_acyclic_graph(G: Graph[_Node]) -> bool: ...
 @_dispatch
+def topological_generations(G: Graph[_Node]) -> Generator[list[_Node], None, None]: ...
+@_dispatch
 def topological_sort(G: Graph[_Node]) -> Generator[_Node, None, None]: ...
 @_dispatch
 def lexicographical_topological_sort(