Add heap-trail partitioning strategy, checks between partitions, and cubes with zero...

Add heap-trail partitioning strategy, checks between partitions, and cubes with zero-level learned literals (#8703)

These changes extend the partition generator to be able to do the following:

Access the order_heap in MiniSat and make partitions from those literals.
Specify a number of checks between partitions. This is relevant for only the revised and strict-cube strategies.
Append zero-level learned literals to the partitions.