feat: improve `HubDataset` image processing support

[jfcalvo]

Description

This PR adds the following changes related to how HubDataset import functionality process rows with images:

• If the image has not format we transform the image to png.
• We convert images to RGB color space to avoid problems with other unsupported color spaces.

Refs https://github.com/argilla-io/roadmap/issues/21

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested

• [x] Manually testing microsoft/cats_vs_dogs dataset.

Checklist

• I added relevant documentation
• I followed the style guidelines of this project
• I did a self-review of my code
• I made corresponding changes to the documentation
• I confirm My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have added relevant notes to the CHANGELOG.md file (See https://keepachangelog.com/)

[codecov[bot]]

Codecov Report

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

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## feat/add-hub-dataset-import #5606 +/- ## ============================================================== Coverage ? 91.15% ============================================================== Files ? 150 Lines ? 6250 Branches ? 0 ============================================================== Hits ? 5697 Misses ? 553 Partials ? 0 ``` | [Flag](https://app.codecov.io/gh/argilla-io/argilla/pull/5606/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io) | Coverage Δ | | |---|---|---| | [argilla-server](https://app.codecov.io/gh/argilla-io/argilla/pull/5606/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io) | `91.15% <100.00%> (?)` | | 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=argilla-io#carryforward-flags-in-the-pull-request-comment) to find out more.

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