Enable sharded cpu resume

[muellerzr]

What does this PR do?

Enables sharded CPU resuming when using FSDP and CPU offloading is enabled

For people potentially googling:

This solves the issue where you could hit a CUDA out-of-memory (CUDA OOM) issue when resuming checkpoints as it would try to load everything onto the GPU, when instead we need to offload on CPU

Fixes # (issue)

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@pacman100

[muellerzr]

Note this won't work right now due to #2757

Edit: reverted and rebased

[HuggingFaceDocBuilderDev]

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