Add descriptive stats to mising tasks and add number of qrels

[imenelydiaker]

Checklist

• Run tests locally to make sure nothing is broken using make test.
• Run the formatter to format the code using make lint.

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I ran some of the missing tasks, and @dokato is running the rest. Also added in this PR the number of qrels (num_relevant_docs) for retrieval datasets (updated 2 tasks for testing).

[Samoed]

Awesome!

[imenelydiaker]

@Samoed can you check the tests? I'm not sure why they're not passing 🤔

[Samoed]

I'll fix them in 2h

[Samoed]

It seems that it tried to merge this branch with 2.0.0 and applied the test from there. In the 2.0.0 branch, I updated the test to check whether a task has metadata or not.

[Samoed]

I think this can be merged now @imenelydiaker

[imenelydiaker]

Thanks @Samoed, merging!