[SofaCore] Revert #2047 for deterministic contacts

[alxbilger]

In this PR, map_ptr_stable_compare is preferred over unordered_map, as it allows reproducible contact response. However, unordered_map is still a lot faster.

#2047 leads to a crash in examples/Components/collision/RayTraceCollision.scn. I suspect the cause of this crash existed before #2047, and that #2047 revealed the crash by processing the contacts in a non-deterministic order. With the non-deterministic order, I can see that the crash does not happen always at the same current time step. It even happened that there was no crash.

Currently, I am not able to fix the crash. But I will continue investigating. As a workaround I restore the stable map to have deterministic contacts. IMO, it hides the cause of the crash.

In the end, I think the stable map should be proposed to the user (as a parameter?) by default. Let's see if we can accelerate it (perhaps with Insimo version).

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• 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.
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[fredroy]

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

[fredroy]

Should be apply it right now, and discuss it in a devmeeting ? or would you want to wait to discuss before merging ?
(IMO we should apply it now)

[alxbilger]

We can apply it now. It will satisfy the CI.
In the meantime, I continue working on the issue.