Heavily improved tree sampling
(Acyclic) tree sampling is now up to 10x faster by....
- early termination by counting available nodes.
- allowing to relax the maximality guarantee, thus avoiding excessive rescue iterations.
Additionally, we improved rescue iterations by adding more nodes at the same time and included root conflict handling into the phase-based control flow (sampling roots is largely equivalent to executing a phase I). Thus,
the conflict-handling code is now at one common place for all cases.