Fault Tolerant Manual: utilities cleanup

[tchaton]

What does this PR do?

This PR re-organizes some utilities and remove dead code.

Find the PoC here: #10568

Parts of #10431

To be merged after #10699

Does your PR introduce any breaking changes? If yes, please list them.

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Did you have fun?

Make sure you had fun coding 🙃

cc @Borda @carmocca @justusschock @awaelchli @ninginthecloud

[ethanwharris]

LGTM 😃