[Helper] PluginManager: support loading from Non-MSVC Multi-Configuration Build

[fredroy]

My case is XCode on macOS but it should be the same problem with ninja multiconfig and other multiconfig generators.

If you compile in Release and in RelWithDebInfo, PluginManager will load the first one it can find recursively from the lib/ directory. So it can try to load Release-compiled plugins while being in RelWithDebInfo (and vice-versa)

This PR adds preprocessor definitions to the builds, and the config is known at compile-time.
For the moment, I just did it in PluginManager and the definitions are not propagated to the other dependencies as I think it may not be a good idea (is it ?).

The only other place I see it can be useful would be for SofaPython3, as the site-packages also uses the split multiconfig directories for its modules. (indeed it is not possible to load SofaPython3 scenes with XCode as it is more or less the same problem)

and I think the file organization in lib, bin, sites-packages, install should be revised...

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Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
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• 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).

[alxbilger]

I discovered recently that our releases are configured with MinSizeRel: https://github.com/sofa-framework/ci/blob/7681010a6382eda0cec2df930c75a1237498f622/scripts/configure.sh#L472
So I suggest to support it as well

[fredroy]

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