Test fewer_resources needs improvement

This test is hard to read and understand.

The tested scenario is the execution of one msg_par_hg profile without communication.
Only one profile is tested, that requires 4 executors. Different mapping are done.

#hosts	cpu_load
1	(4)
2	(2,2)
3	(2,1,1)
4	(1,1,1,1)

In this case, the execution time is expected to be slowed down by a factor of max(cpu_load).
Making this explicit would be better than just writing the expected values in the test.

It would also be interesting to split this check by profile type, as this behavior is only expected for computation-only msg_par_hg profiles.