algo: Occurrences and Run for Z-Automata on PrefixBarTree

For efficiency, let's implement runs of deterministic Z-Automata also
on linearised unranked tree.

Based on my testing with a tree constructed from sprotall.xml [1] the
run is ~15 % faster than a run over UnrankedTree.

[1]: https://research.cs.wisc.edu/niagara/data.html