Ensure we cover multi-threaded use in regression tests

[sylvlecl]

Context When working on removal of space concept, we broke the thread safety in hydro management class, but this did not break any regression tests. Therefore, it seems that multi-threaded behaviour is not well enough covered by regression tests.

Goal Ensure non regression on multi-threaded behaviour, by having regression tests with parallelism enabled for all features that might use it.