With the changes in this MR I have been able to run successfully the avalanche scheduler tests that were failing in !1470 (closed) with an older version of TBB (2020.3) and a newer one (oneTBB, 2021.10 which is not from 2021 but was released a few months ago). I also checked that changing the number of threads passed to the AvalancheSchedulerSvc is indeed in effect since it was related to one of the changes when initializing task_arena.
Fixes #270 (closed)
Supersedes !1470 (closed)