[examples] max samples can't be bigger than the len of dataset
Starting with `datasets==1.18.4` an exception is raised when `ds.select(myrange)` is called and `myrange` includes indices larger than the length of the dataset. This impacts all our examples, e.g.:

```
stderr: Traceback (most recent call last):
stderr:   File "/mnt/nvme0/code/huggingface/transformers-master/examples/pytorch/translation/run_translation.py", line 624, in <module>
stderr:     main()
stderr:   File "/mnt/nvme0/code/huggingface/transformers-master/examples/pytorch/translation/run_translation.py", line 436, in main
stderr:     train_dataset = train_dataset.select(range(data_args.max_train_samples))
stderr:   File "/home/stas/anaconda3/envs/py38-pt111/lib/python3.8/site-packages/datasets/arrow_dataset.py", line 486, in wrapper
stderr:     out: Union["Dataset", "DatasetDict"] = func(self, *args, **kwargs)
stderr:   File "/home/stas/anaconda3/envs/py38-pt111/lib/python3.8/site-packages/datasets/fingerprint.py", line 458, in wrapper
stderr:     out = func(self, *args, **kwargs)
stderr:   File "/home/stas/anaconda3/envs/py38-pt111/lib/python3.8/site-packages/datasets/arrow_dataset.py", line 2601, in select
stderr:     _check_valid_indices_value(int(max(indices)), size=size)
stderr:   File "/home/stas/anaconda3/envs/py38-pt111/lib/python3.8/site-packages/datasets/arrow_dataset.py", line 573, in _check_valid_indices_value
stderr:     raise IndexError(
stderr: IndexError: Invalid value 15 in indices iterable. All values must be within range [-11, 10].
```

This PR is trying to fix the issue across all pytorch examples with:

```
find examples -type f -name "*.py" -exec perl -pi -e 's|^(\s+)(eval_dataset = eval_dataset.select.range.data_args.max_eval_samples..)|$1max_eval_samples = min(len(eval_dataset), data_args.max_eval_samples)\n$1eval_dataset = eval_dataset.select(range(max_eval_samples))|' {} \;
find examples -type f -name "*.py" -exec perl -pi -e 's|^(\s+)(eval_examples = eval_examples.select.range.data_args.max_eval_samples..)|$1max_eval_samples = min(len(eval_examples), data_args.max_eval_samples)\n$1eval_examples = eval_examples.select(range(max_eval_samples))|' {} \;
find examples -type f -name "*.py" -exec perl -pi -e 's|^(\s+)(predict_dataset = predict_dataset.select.range.data_args.max_predict_samples..)|$1max_predict_samples = min(len(predict_dataset), data_args.max_predict_samples)\n$1predict_dataset = predict_dataset.select(range(max_predict_samples))|' {} \;
find examples -type f -name "*.py" -exec perl -pi -e 's|^(\s+)(test_dataset = test_dataset.select.range.data_args.max_eval_samples..)|$1max_eval_samples = min(len(test_dataset), data_args.max_eval_samples)\n$1test_dataset = test_dataset.select(range(max_eval_samples))|' {} \;
find examples -type f -name "*.py" -exec perl -pi -e 's|^(\s+)(train_dataset = train_dataset.select.range.data_args.max_train_samples..)|$1max_train_samples = min(len(train_dataset), data_args.max_train_samples)\n$1train_dataset = train_dataset.select(range(max_train_samples))|' {} \;
```

I may have missed some cases, but this should cover most of it.

This PR only adjusts the pytorch examples. 

@sgugger 
_The documentation is not available anymore as the PR was closed or merged._<|||||>sure, replayed for tf/flax as well.<|||||>Very nice of you, thanks a lot!

You caught some research projects in the change, but it's more defensive, so fine to merge.