The previous implementation has the notion of 'task ready' that is
removed from the new implementation.

When a task is created, it initializes some data structures and whatever
and then marks itself ready. Then it waits for all the other tasks to
be also ready. Then it does what it has to do.

The task creator creates all the tasks, then waits for each of them to
be ready then it sets a global variable to signal all the tasks that
all the other tasks are ready and that they can start their work.

The new ITTI implementation wants to be API-compatible with the previous
implementation but completely fails to respect this initialization
mechanism, leading to various random crashes.

We already observe some failures in the CI testbench with the basic
simulator.

This commit is not to be integrated into the develop branch but is done
to check if the analysis above is correct.

If it is then the basic simulator should work properly in the CI, as it
more or less used to do with the previous IITI implementation.

And then we need a proper fix. What is done here is not really satisfying.
(But can go into develop if no cleaner solution is found.)

Let's see...