[Core] Add a level 3 sleep/wake_up that offloads tensors to disk

[manoelmarques]

Add Level 3 sleep mode that will offload the model weights to disk and discard the kv cache.

The model weights are not backed up in CPU memory and the content of kv cache is forgotten.

Level 3 sleep helps use minimum CPU memory and loads efficiently from disk when woken up.

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[youkaichao]

I'm hesitant to do it. There are too many things to consider, in terms of disk, like the location of the disk to use, whether or not saving all tensors in one file ...

I would recommend you rewrite the sleep (level=1) logic for your use case, and keep it your own. I don't think this complexity is a good fit for the upstream.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @manoelmarques.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @manoelmarques.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @manoelmarques.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork