Support features in metadata configs

[albertvillanova]

Support features in metadata configs, like:

configs:
  - config_name: default
    features:
      - name: id
        dtype: int64
      - name:  name
        dtype: string
      - name: score
        dtype: float64

This will allow to avoid inference of data types.

Currently, we allow passing this information in the dataset_info (instead of configs) field, but this is not intuitive and it is not properly documented.

TODO:

• Document usage

[HuggingFaceDocBuilderDev]

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[albertvillanova]

The CI issue is unrelated:

• CI is broken for deps-latest #7183

[lhoestq]

lgtm, let's see if it works and we can add it to the datasets hub documentation for the viewer (e.g. "how to enforce certain column types in the viewer")