[Core] STL parallelism support

[alxbilger]

Introduce flags to know if STL parallelism is supported (see https://github.com/sofa-framework/BeamAdapter/pull/50), and an example on how to use it.

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[damienmarchal]

Thanks for the interesting PR.

It is unclear to me why using macros. It was thinking that these features are c++17 and we agreed sofa to on its way to c++20.

[fredroy]

Thanks for the interesting PR.

It is unclear to me why using macros. It was thinking that these features are c++17 and we agreed sofa to on its way to c++20.

For the moment, even if a compiler/std lib supports c++17, it does not mean for sure it supports stl parallelism unfortunately. I dont remember which one but one of the compiler of our "base" OSes on the CI did not support it. (mac clang or ubuntu gcc)

[alxbilger]

[ci-build][with-all-tests]

[alxbilger]

An alternative is to support only compilers supporting parallel algorithms

[fredroy]

Giving more info: it was not supported for Ubuntu2004 while I implemented this feature in BeamAdapter

https://github.com/sofa-framework/BeamAdapter/actions/runs/2880398323 (no more logs unfortunately)

[alxbilger]

Postponed until support of Ubuntu 20.04 is dropped