Make image dirs data format streamable

[itrushkin]

Summary

Geti requires all data formats to be streamable, i. e. generate dataset items on demand.
This PR allows streaming for image dir format.

How to test

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

[sooahleex]

This also looks good to me, but isn't there any need to add unit tests for this?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.03%. Comparing base (9bdf8de) to head (1874a9c).
Report is 8 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1576      +/-   ##
===========================================
- Coverage    81.03%   81.03%   -0.01%     
===========================================
  Files          276      278       +2     
  Lines        32430    32471      +41     
  Branches      6595     6599       +4     
===========================================
+ Hits         26280    26312      +32     
- Misses        4696     4705       +9     
  Partials      1454     1454              

Flag	Coverage Δ
ubuntu-20.04_Python-3.10	81.02% <100.00%> (-0.01%)	⬇️
windows-2022_Python-3.10	81.00% <100.00%> (-0.01%)	⬇️

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