Add YOLO Loose format

[vinnamkim]

Summary

• Ticket no. 104512
• Currently, YOLO format requires too strict directory structure and too many meta files.
• Add YoloLooseImporter and revisit notebooks/06_tiling.ipynb to use it.
• Add documentation for YoloLoose format.

How to test

I added tests to cover this change and made some refactoring of the existing tests by moving some tests to tests/unit/data_formats/test_yolo_format.py.

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

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) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

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Codecov Report

Patch coverage: 84.75% and project coverage change: +0.01 🎉

Comparison is base (21755d3) 78.59% compared to head (4596f11) 78.60%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #856      +/-   ##
===========================================
+ Coverage    78.59%   78.60%   +0.01%     
===========================================
  Files          198      200       +2     
  Lines        24377    24497     +120     
  Branches      4932     4950      +18     
===========================================
+ Hits         19159    19257      +98     
- Misses        4118     4132      +14     
- Partials      1100     1108       +8     

Flag	Coverage Δ
macos-11_Python-3.8	77.95% <84.75%> (+0.01%)	⬆️
ubuntu-20.04_Python-3.8	78.60% <84.75%> (+0.01%)	⬆️
windows-2019_Python-3.8	78.54% <84.75%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
datumaro/components/format_detection.py	93.54% <ø> (ø)
datumaro/components/importer.py	89.68% <ø> (ø)
datumaro/plugins/data_formats/yolo/importer.py	81.39% <81.39%> (ø)
datumaro/plugins/data_formats/yolo/base.py	87.50% <84.74%> (-2.33%)	⬇️
datumaro/components/dataset_base.py	74.69% <100.00%> (ø)
datumaro/components/media.py	83.56% <100.00%> (ø)
datumaro/plugins/data_formats/yolo/format.py	100.00% <100.00%> (ø)
datumaro/util/definitions.py	100.00% <100.00%> (ø)
datumaro/util/os_util.py	66.66% <100.00%> (+1.96%)	⬆️

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[wonjuleee]

Sorry for late response, but it looks good to me! Please merge this.