Handling tfds import part to prevent cli error when installing datumaro with default option only

[jihyeonyi]

Summary

This is a bug fix for the issue #1444

How to test

1. uninstall tfds if it exists.
2. install datumaro with default option (pip install datumaro[default] or pip install -e .[default])
3. run datum --version or datum --help

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2024 Intel Corporation
#
# SPDX-License-Identifier: MIT

[vinnamkim]

@wonjuleee @yunchu
This hotfix should be released in 1.6.1 as fast as possible. Any system not installing tfds and installing Datumaro by pip install datumaro cannot execute every CLI command in 1.6.0.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (releases/1.6.0@6988d69). Click here to learn what that means.

Files	Patch %	Lines
src/datumaro/components/extractor_tfds.py	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##             releases/1.6.0    #1454   +/-   ##
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  Coverage                  ?   80.66%           
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  Files                     ?      271           
  Lines                     ?    30722           
  Branches                  ?     6204           
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  Hits                      ?    24783           
  Misses                    ?     4538           
  Partials                  ?     1401           

Flag	Coverage Δ
ubuntu-20.04_Python-3.10	80.64% <66.66%> (?)
windows-2022_Python-3.10	80.64% <66.66%> (?)

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[yunchu]

LGTM