Run offline and online simulations in the tests

The goal of this change is to run both the offline and online simulations in the test and compare their simulated times. An error is raised if one of the simulations fails or if the timings are too different.

For that, I implemented a simple Python script that handles the execution and comparison. Since the *.org file should remain understandable by a newcomer, I kept the original smpirun command as a comment.

Currently, I only changed the HPL *.org file, if you are happy with the proposed change I can do the same with the others (at least those for which the offline simulation works).