Include entity positions as feature in ReCoRD
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_4479). All of your documentation changes will be reflected on that endpoint.
https://huggingface.co/datasets/super_glue/viewer/record/validation

TLDR: We need to record entity positions, which included in the source data but excluded by the loading script, to enable efficient and effective training for ReCoRD.

Currently, the loading script ignores the entity positions ("entity_start", "entity_end") and only records entity text. This might be because the training method of the official baseline is to make n training instance from a datapoint by replacing \"\@ placeholder\" in query with each entity individually.

But it increases the already heavy computation by multiple folds. So DeBERTa uses a method that take entity embeddings by their positions in passage, and thus make one training instance from one datapoint. It is way more efficient and proved effective for ReCoRD task.