[MultiThreading] FIX: add createSubelements param in MeshGmshLoader

[guparan]

This fix was already applied to examples/Components/forcefield/TriangularForceFieldComparison.scn
See 28c8b68

Sorry but I can't explain why this fix was needed in the first place.
If someone could, that would be great 👍

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This PR:

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

Reviewers will merge only if all these checks are true.

[guparan]

[ci-build][with-scene-tests]

[guparan]

[ci-build][with-scene-tests]

[epernod]

createSubelements="true": Divide all n-D elements into their (n-1)-D boundary elements (e.g. tetrahedra to triangles).
Meaning: for a triangulation, create all edges.

In this case the mesh file had only edges of the border but the FF were using all edges of the mesh.

[epernod]

This PR fix the crash.

But some work is needed on the meshloader to avoid this behavior.