Hierarchies with multiple parents

[HeikoTheissen]

• Multiple parents per node are allowed, leading to duplicate nodes in the result set.
• In the result set, Aggregation.UpPath annotation contains the node identifiers of one sequence of parents (or ancestors).
• The optional parameter $S$ is removed from ancestors and descendants (see Remove optional parameter from ancestors and descendants odata-abnf#100).
• The optional parameter $S$ in traverse defines the start nodes for the traversal (default is start node = root node).
• The optional parameter $S$ in rolluprecursive is needed for rolling up "actual totals" (as opposed to "visual totals", see example 68).

[GeraldKrause]

Approved with the changes discussed in TC call 2023-06-28