[Helper] Add Taskflow dependency to CMake build system

[alxbilger]

Integrate Taskflow as a header-only library, update CMake configuration to locate and fetch Taskflow if necessary, and include relevant headers.

taskflow: https://github.com/taskflow/taskflow

More information:

• https://taskflow.github.io/
• https://www.youtube.com/watch?v=MX15huP5DsM

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Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[damienmarchal]

It remind me so much something we did with PJBensoussan around 2006 in SOFA.

[alxbilger]

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

[olivier-roussel]

Modern cmake usage is more a suggestion here (my commits 05691e0 and cec0c7a ). Both solutions work fine and looks good to me. It was mainly driven by the idea of being consistent with cmake config files provided by the Taskflow library itself.
Don't know if anybody has an opinion about that... I can revert these commits if necessary

[alxbilger]

About cec0c7a, it is was a conclusion in the last dev meeting. So, thank you for having done the job!

Another question: is there something to do regarding the package/installation process?

[olivier-roussel]

The only thing I think is still missing here is the find package for the generated cmake config file of Sofa.Helper, i.e. adding in the Sofa.HelperConfig.cmake.in :

if(NOT TARGET Taskflow::Taskflow)
    sofa_find_package(Taskflow QUIET REQUIRED)
endif()

But strangely, find_package calls for other required libs (Json, STB, DiffLib) are missing as well here. So either it is an omission, either I am wrong and missing something...
Ok my bad: Json, STB and DiffLib are not using targets so they do not need to be explicitly found here. Everything is OK for them. We just need this find_pacakge in the Sofa.HelperConfig.cmake.in if we use the modern cmake version.

[olivier-roussel]

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

[olivier-roussel]

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

[olivier-roussel]

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

[olivier-roussel]

Just for information, there would/will be some extra steps necessary after looking for the Taskflow package in the Sofa.Helper CMakeLists.txt to install the library (headers + cmake config files) in the case of building the binary package on Windows. But this when we'll have migrated our Windows support on Pixi and it's purely related to it, so I'll do it in #5252.