ParallelRandomRestartHillClimber uses the same instances of its SuccessorGenerator/SuccessorSelector across worker threads

[jlat96]

ParallelRandomRestartHillClimber uses the same instances of its SuccessorGenerator/SuccessorSelector across worker threads causing concurrency issues. Instead of relying on the implementation of ISuccessorGenerator to account for concurrency, use a new instance of the object for each worker thread.