[Spaces] Add support for mounted volumes

[Wauplin]

Related to server-side PR (private link) cc @XciD

This PR adds set_space_volumes and delete_space_volumes and updates the Spaces guide.

I also took the opportunity to deprecate the persistent storage methods.

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Tested manually with https://huggingface.co/spaces/Wauplin/test-volumes

>>> get_space_runtime("Wauplin/test-volumes").volumes
[Volume(type='bucket', source='Wauplin/test-volumes-storage', mount_path='/data', revision=None, read_only=False, path=None)]

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Note

Medium Risk
Introduces new Space runtime/mutation API endpoints (/volumes) and deprecates existing storage methods/options, which can affect client integrations and backwards compatibility if callers rely on space_storage behavior.

Overview
Adds first-class mounted volumes support for Spaces via new HfApi.set_space_volumes (PUT) and HfApi.delete_space_volumes (DELETE), plus exposes mounted volumes on SpaceRuntime.volumes using a shared Volume dataclass.

Deprecates persistent storage configuration and APIs: space_storage on create_repo/duplicate_repo and the request_space_storage/delete_space_storage methods now emit deprecation warnings; CLI docs/option help mark --storage as deprecated and the Spaces guide is updated to document volumes instead of persistent storage.

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[Wauplin]

✔️ (ready for review @hanouticelina)

[hanouticelina]

Thanks!
if possible, it would be nice to have tests for set_space_volumes and delete_space_volumes (usually helpful to catch any server-side changes we might miss )

[hanouticelina]

no CLI replacement yet right?

[Wauplin]

no not yet (see https://github.com/huggingface-internal/moon-landing/pull/17543). I'll handle it in a separate PR once it's released server-side

[Wauplin]

if possible, it would be nice to have tests for set_space_volumes and delete_space_volumes (usually helpful to catch any server-side changes we might miss )

well that's the problem usually with the Space API, we can't test it on staging. At some point in the past we had tests on production but it was unreliable and annoying to run on contributed PRs. So we just have to hope the API will stay stable ^^

[hanouticelina]

Thank you!