[all] More std::cout to msg_* cleaning

[damienmarchal]

This is the Defrost cleaning week29 with...as usual a lot of std:cout and dead code removal.
Shouldn't break anything.
In case some component are too verbose please tell us.

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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]

Thank you @SofaDefrost for these cleaning PRs.
LGTM, mainly by reading CI results though since it's quite hard to review such a massive diff.