feat: fix importing datasets features mapped as chat fields

[jfcalvo]

Description

Using the dataset https://huggingface.co/datasets/mlabonne/ultrachat_200k_sft we have found that the import feature was not mapping correctly the message feature.

In order to fix this I'm improving with this PR how the feature values casting is done, checking if the features are instances of certain feature classes instead of using the _type method.

I have also added a new test importing the mlabonne/ultrachat_200k_sft dataset and using chat fields.

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] Adding new tests to the suite.

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:

Project coverage is 91.18%. Comparing base (bc720c2) to head (0bc9a31). Report is 1 commits behind head on feat/argilla-direct-feature-branch.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## feat/argilla-direct-feature-branch #5611 +/- ## ====================================================================== - Coverage 91.20% 91.18% -0.02% ====================================================================== Files 150 150 Lines 6253 6251 -2 ====================================================================== - Hits 5703 5700 -3 - Misses 550 551 +1 ``` | [Flag](https://app.codecov.io/gh/argilla-io/argilla/pull/5611/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/5611/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=argilla-io) | `91.18% <100.00%> (-0.02%)` | :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=argilla-io#carryforward-flags-in-the-pull-request-comment) to find out more.

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