Add a new CLI command: datum format

[vinnamkim]

Summary

• This PR resolves https://jira.devtools.intel.com/browse/CVS-144954 and CLI Format Documentation #1545
• Add a new CLI command: datum format. It displays a list of data format names supported by Datumaro. It can be useful for quick reference of data format name used for other CLI command such as datum convert -if <data-format> -f <data-format>.

How to test

Added unit tests as well.

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

[codecov]

Codecov Report

Attention: Patch coverage is 70.73171% with 12 lines in your changes missing coverage. Please review.

Project coverage is 81.03%. Comparing base (9bdf8de) to head (5438516).
Report is 6 commits behind head on develop.

Files	Patch %	Lines
src/datumaro/cli/__main__.py	0.00%	11 Missing ⚠️
src/datumaro/cli/helpers/format.py	96.55%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1570      +/-   ##
===========================================
- Coverage    81.03%   81.03%   -0.01%     
===========================================
  Files          276      278       +2     
  Lines        32430    32468      +38     
  Branches      6595     6599       +4     
===========================================
+ Hits         26280    26309      +29     
- Misses        4696     4705       +9     
  Partials      1454     1454              

Flag	Coverage Δ
ubuntu-20.04_Python-3.10	81.02% <70.73%> (-0.01%)	⬇️
windows-2022_Python-3.10	81.00% <70.73%> (-0.01%)	⬇️

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[wonjuleee]

Great work! Many thanks.