http_backoff retry with SliceFileObj

[hlky]

Retry mechanism of http_backoff doesn't work from lfs_upload->_upload_multi_part->_upload_parts_iteratively path, data is consumed after the first attempt when using SliceFileObj because io_obj_initial_pos should be set and reset on retry, io_obj_initial_pos is not set due to isinstance(kwargs["data"], io.IOBase).

This PR changes the check to isinstance(kwargs["data"], (io.IOBase, SliceFileObj)) and moves SliceFileObj to utils._lfs to avoid circular import:

huggingface_hub> python utils/check_inference_input_params.py
Error importing huggingface_hub.inference._client: cannot import name 'fix_hf_endpoint_in_url' from partially initialized module 'huggingface_hub.utils' (most likely due to a circular import) (huggingface_hub\src\huggingface_hub\utils\__init__.py)
Traceback (most recent call last):
  File "huggingface_hub\utils\check_inference_input_params.py", line 28, in <module>
    from huggingface_hub import InferenceClient
  File "huggingface_hub\src\huggingface_hub\__init__.py", line 530, in __getattr__
    submod = importlib.import_module(submod_path)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "Python311\Lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "huggingface_hub\src\huggingface_hub\inference\_client.py", line 57, in <module>
    from huggingface_hub.inference._common import (
  File "huggingface_hub\src\huggingface_hub\inference\_common.py", line 53, in <module>
    from ..utils import (
  File "huggingface_hub\src\huggingface_hub\utils\__init__.py", line 54, in <module>
    from ._http import (
  File "huggingface_hub\src\huggingface_hub\utils\_http.py", line 33, in <module>
    from huggingface_hub.lfs import SliceFileObj
  File "huggingface_hub\src\huggingface_hub\lfs.py", line 32, in <module>
    from .utils import (
ImportError: cannot import name 'fix_hf_endpoint_in_url' from partially initialized module 'huggingface_hub.utils' (most likely due to a circular import) (huggingface_hub\src\huggingface_hub\utils\__init__.py)

Usage of SliceFileObj in other areas is updated to import from utils._lfs.

Closes #2539

[Wauplin]

This is a very sensible fix! Thanks for tracking that down @hlky and suggesting a PR. It's ready to merge "as is" as soon as CI passes :)

EDIT: next time if we again have an issue with this, we could use a Protocol + runtime_checkable to check if .seek() and .tell() exist. (Never used this solution before and still think an explicit ref to SliceFileObj is better, just mentioning it for curiosity)

[Wauplin]

Failing tests are unrelated so let's merge this PR :)