Improve error message for MPI implementations incompatible with Julia multi-threading

[alexandrebouchard]

Context: see B2b in the first comment in #30

Proposed improvement:

1. reintroduce the ubuntu-based test cases to ensure B2b is replicated and not already fixed by ubuntu updating their open mpi release
2. change the system-binary based tests to use setup_mpi(), i.e.

   Pigeons.jl/src/submission/MPISettings.jl

   Line 56 in 4a32dea

   function setup_mpi(settings::MPISettings)

3. In setup_mpi(), run a test based on https://github.com/Julia-Tempering/Pigeons.jl/blob/investigate-segfault/test/gc_test.jl as part of the setup, set a flag in MPISetting encoding if the multithreading+GC option will be supported. If not, print a warning
4. when submitting, show the warning again if multithreading+GC+MPISetting flag.
5. add option to disable GC in ChildProcesses
6. Test these functionalities