Fix project level CVAT for images format import

[vinnamkim]

Summary

• Ticket no. 109743
• While writing the OpenVINO blog posting draft, I found that importing the project level CVAT for images format is incorrect for an image path and the existing unit test has been not testing this.
• Fix an incorrect image file path when importing the project level CVAT for images format dataset
• This will be merged into releases/1.2.0 to make datumaro==1.2.1.

How to test

I updated the existing test also.

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

[codecov-commenter]

Codecov Report

Patch coverage: 77.77% and project coverage change: -0.01 ⚠️

Comparison is base (2b7fb35) 78.70% compared to head (20f3ee8) 78.70%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           releases/1.2.0     #980      +/-   ##
==================================================
- Coverage           78.70%   78.70%   -0.01%     
==================================================
  Files                 231      231              
  Lines               26420    26425       +5     
  Branches             5258     5260       +2     
==================================================
+ Hits                20795    20797       +2     
- Misses               4400     4401       +1     
- Partials             1225     1227       +2     

Flag	Coverage Δ
macos-11_Python-3.8	77.72% <77.77%> (-0.01%)	⬇️
ubuntu-20.04_Python-3.8	78.67% <77.77%> (-0.02%)	⬇️
windows-2019_Python-3.8	78.58% <77.77%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
datumaro/plugins/data_formats/cvat/base.py	91.66% <77.77%> (+0.18%)	⬆️

... and 1 file with indirect coverage changes

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[sooahleex]

Looks good to me.