Multilabel metrics not supported
Hi @GuillemGSubies, thanks for reporting.

I have made a PR to fix this issue and allow metrics to be computed also for multilabel classification problems. Looks nice, thank you very much! 🚀  Sorry for reopening but I just noticed that the `_compute` method for the F1 metric is still not good enough for multilabel problems:

https://github.com/huggingface/datasets/blob/92a3ee549705aa0a107c9fa5caf463b3b3da2616/metrics/f1/f1.py#L115

Somehow we should be able to change the parameter `average` at least @GuillemGSubies, the parameter `average` passed to `_compute` is then passed to `f1_score`. This is right.
When I try to use a metric like F1 macro I get the following error:

```
TypeError: int() argument must be a string, a bytes-like object or a number, not 'list'
```
There is an explicit casting here:

https://github.com/huggingface/datasets/blob/fc79f61cbbcfa0e8c68b28c0a8257f17e768a075/src/datasets/features.py#L274

And looks like this is because here

https://github.com/huggingface/datasets/blob/fc79f61cbbcfa0e8c68b28c0a8257f17e768a075/metrics/f1/f1.py#L88

the features can only be integers, so we cannot use that F1 for multilabel. Instead, if I create the following F1 (ints replaced with sequence of ints), it will work:

```python
class F1(datasets.Metric):
    def _info(self):
        return datasets.MetricInfo(
            description=_DESCRIPTION,
            citation=_CITATION,
            inputs_description=_KWARGS_DESCRIPTION,
            features=datasets.Features(
                {
                    "predictions": datasets.Sequence(datasets.Value("int32")),
                    "references": datasets.Sequence(datasets.Value("int32")),
                }
            ),
            reference_urls=["https://scikit-learn.org/stable/modules/generated/sklearn.metrics.f1_score.html"],
        )

    def _compute(self, predictions, references, labels=None, pos_label=1, average="binary", sample_weight=None):
        return {
            "f1": f1_score(
                references,
                predictions,
                labels=labels,
                pos_label=pos_label,
                average=average,
                sample_weight=sample_weight,
            ),
        }
```
