Adding _safe_open_handle.

[Narsil]

What does this PR do?

Add surface with file descriptors.

Checks that the object has a fileno() and a name, and reads the file.

loaded = {}
with fs.open("fs.safetensors", "rb") as f:
    with safe_open_handle(f, framework="np", device="cpu") as g:
        for key in g.keys():
            loaded[key] = g.get_tensor(key)

Fixes # (issue) or description of the problem this PR solves.

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[ArthurZucker]

LGTM!