Add optional s3fs / gcfs as optional dependencies

[praateekmahajan]

Is your feature request related to a problem? Please describe.
If customers want to use NeMo Curator on Cloud we should add optional groups as s3 or gc that installs the correct version inline with our existing fsspec installation. If users install themselves using pip, it might be possible that Curator needs fsspec=2024.12 while pip as an additional install of s3fs installs 2025.12

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[nightcityblade]

Hi, I'd like to work on this. I'll submit a PR shortly.

[nightcityblade]

I prototyped the two cloud-storage extras, but adding gcsfs requires a broad lockfile update (multiple Google Cloud transitive packages), so this is larger than the small focused change I can responsibly submit here. I'm stepping back and unclaiming rather than leaving the lockfile inconsistent.

[nightcityblade]

Hi, I'd like to revisit and work on this now that the dependency set has evolved. I'll submit a focused PR shortly if the lockfile remains consistent.

[nightcityblade]

I rechecked this against current main. Adding the gcsfs extra requires six to seven new Google/OAuth packages, and regenerating the required lockfile changes about 900 lines; omitting that update makes the lock check fail. This is still larger than a focused dependency-metadata change, so I'm stepping back and unclaiming rather than submitting a partial or inconsistent PR.