[ray] Fix `datasets_modules` ImportError with Ray Tune
Author: Yard1
Pull request: yes

# What does this PR do?

This PR fixes an ImportError throws due to `datasets_modules` not being loaded on Ray Actors when tuning hyperparamters with Ray, fixing the following issues:
[huggingface/blog#106](https://github.com/huggingface/blog/issues/106)
[huggingface/transformers#11565](https://github.com/huggingface/transformers/issues/11565)
https://discuss.huggingface.co/t/using-hyperparameter-search-in-trainer/785/34
https://discuss.huggingface.co/t/using-hyperparameter-search-in-trainer/785/35

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Fixes #11565


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Comments:
@richardliaw @pvcastro 

Great! @richardliaw , another approval is still required?

@sgugger @LysandreJik could you help take a look :)