✨ Parallelize asnchronous calls to the SAT solver

[pehamTom]

What's the problem this feature will solve?

The iterative_search_with_timeout method in the ft_stateprep module makes repeated calls to a function with a certain timeout and tries to iteratively increase a parameter until the method does not time out. This is used to quickly search for a parameter where a SAT solver can find a satisfying assignment.

To enforce the timeout, the function is started as a separate process and is killed upon exceeding the timeout limit. Many of these calls can be executed in parallel and once a satisfying assignment is found for one parameter all other processes can be killed. Technically one does not need to kill all processes for this. One can also terminate all calls that use a larger parameter (for satisfying assignments) or smaller parameter (for proofs of UNSAT).

Describe the solution you'd like

When calling iterative_search_with_timeout, the calls should be made concurrently. An n_threads parameter would also be useful in this case.