The satsolver is reatined and only updated with new clauses for every
state that is generated out of a core. Once the core becomes Open (as
opposed to expandable), the solver is no longer needed.

This patch makes the solver a `Solver option` and gets it deallocated
once no longer needed and resets the hashtable (makes it empty and zero
size) to save memory. This saves about 60% memory usage on some extreme
cases (e.g. exp_unsat from the CTL Benchmark set)

Instead of some calculation based of finishing on normal Cores really
count proper Open States

Assumption doesn't hold true currently

With Sat states only treated like other states in the second fixpoint
iteration, the outer fixpoint was not ncessarily monononously decreasing
causing wrong results when in the first round the same number of nodes
got removed as added due to sat states.

Acceptance test for cores is ∃ which is safe to use when non or only
some child states are created tus far

Should actually happen when the State changes from `Expandable` to
`Open` and trigger the propagateSatMu but for now just do it in
propagateSatMu so we can observe the algorithm working.

Not only finishing cycles but also plain sat nodes may cause a node to
be satisfiable