Fault Tolerant Manual: Add stateful dataloader iter

[tchaton]

What does this PR do?

Find the complete PoC here: #10568

Parts of #10431

To be merged after

• Fault Tolerant Manual: Add _SupportsStateDict to validate a class is stateful #10646

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cc @Borda @carmocca @justusschock @awaelchli @ninginthecloud

[justusschock]

LGTM!

One general and one minor question.

[SeanNaren]

Looks good. imo we should offer a mixin class to add state_dict an load_state_dict for samplers/datasets, primarily out of good practice. But this can come at a later date :)