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

• [x] 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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/openvinotoolkit/datumaro/pull/1576/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | Coverage Δ | | |---|---|---| | [ubuntu-20.04_Python-3.10](https://app.codecov.io/gh/openvinotoolkit/datumaro/pull/1576/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | `81.02% <100.00%> (-0.01%)` | :arrow_down: | | [windows-2022_Python-3.10](https://app.codecov.io/gh/openvinotoolkit/datumaro/pull/1576/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | `81.00% <100.00%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit#carryforward-flags-in-the-pull-request-comment) to find out more.

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