Implement utils for Runnables instead of Callables

[todo]

mito/src/main/java/de/tum/bgu/msm/util/concurrent/ConcurrentExecutor.java

Lines 77 to 82 in 65ecd0f

	//TODO: Implement utils for Runnables instead of Callables
	for(Future<T> future: futures) {
	future.get();
	}
	return futures;
	} catch (InterruptedException | ExecutionException e) {

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This issue was generated by todo based on a TODO comment in 65ecd0f when #77 was merged. cc @msmobility.