Add RVL-CDIP dataset

Resolves #2762 

Dataset Request : Add RVL-CDIP dataset [#2762](https://github.com/huggingface/datasets/issues/2762)
This PR adds the RVL-CDIP dataset.

The dataset contains Google Drive link for download and wasn't getting downloaded automatically, so I have provided manual_download_instructions.
- I have added the dummy_data.zip as well.

Needed inputs on how I can run the real data and the dummy data tests for datasets with manual download ?

Inputs and suggestions for improvement are welcome. Thank you.

Comments:
_The documentation is not available anymore as the PR was closed or merged._

Thanks a lot for inputs. I'll use the URL suggested and check.

>  we need to implement the streamable (can't use os.path.join) and the non-streamable versions of _generate_examples.

Sure. I will check the reference and try this out, will get back to you if I face any issues.

> The labels-only data file URL doesn't work for me, so feel free to ask the authors whether they are OK with us hosting the file on the Hub/S3 (to speed up the streamable version)

Just checked. The author (Adam Harley) has responded positively and allowed us to host the file. Do I share the file with you for hosting it on Hub/S3 ?

> Just checked. The author (Adam Harley) has responded positively and allowed us to host the file. Do I share the file with you for hosting it on Hub/S3 ?

Yes, feel free to e-mail me the file. Then I'll create a repo under my namespace and push the file there. We run a GH action on a GH dataset after merging to create its repo on the Hub, so after this PR is merged, I'll push the file to the "official" namespace and update the download link.

> You can use this URL to avoid manual download: https://drive.google.com/uc?export=download&id=0Bz1dfcnrpXM-MUt4cHNzUEFXcmc

For some reason, the direct download doesn't seem to work for me even with this URL. 
```
Downloading and preparing dataset rvl_cdip/default to ~/.cache/huggingface/datasets/rvl_cdip/default/1.0.0/ea152149e06310d60a9ef3c3020199dd4780bb952a773ba5aac6b57d59f12628...
Downloading data files: 100%|█████████████████████████████████████████████████████| 1/1 [00:00<00:00, 6307.22it/s]
{'rvl-cdip': '~/.cache/huggingface/datasets/downloads/07ef956a33750078d570d76fefe9fed49f7dc32ecf6e872d690de11e66bbe869'}
```
And this directory does not exist. Am I doing something wrong ?
To verify, I tried using [gdown](https://github.com/wkentaro/gdown) for the above URL, we get the following : 
```
Access denied with the following error:

        Cannot retrieve the public link of the file. You may need to change
        the permission to 'Anyone with the link', or have had many accesses. 

You may still be able to access the file from the browser:
```
----

> Yes, feel free to e-mail me the file. Then I'll create a repo under my namespace and push the file there. We run a GH action on a GH dataset after merging to create its repo on the Hub, so after this PR is merged, I'll push the file to the "official" namespace and update the download link.

Got it. I've sent you an email with the file. Thank you.

Actually this URL works for direct download :
`https://drive.google.com/uc?export=download&confirm=pbef&id=0Bz1dfcnrpXM-MUt4cHNzUEFXcmc`
Ref : https://github.com/wkentaro/gdown/issues/146#issuecomment-1042382215

I'm working on the streamable versions of _generate_examples as well, will update you regarding this.

Google Drive is a tricky host, and it's easy to exceed daily download quota limits, so if we are allowed to host the `rvl-cdip.tar.gz` file, I can push it to the Hub.

Just checked, the authors have agreed. He mentioned that he had complaints about the GDrive link.
You can push it to the Hub and share the link. :)

I have added :
- streaming support for rvl-cdip.tar.gz file. [ Need to test this ]

Is it possible for you to upload the train.txt, test.txt, val.txt files separately to the Hub instead of labels_only.tar.gz file.
Currently during the tests in stream mode, we get : 
`NotImplementedError: Extraction protocol for TAR archives like 'https://huggingface.co/datasets/mariosasko/rvl_cdip/resolve/main/labels_only.tar.gz' is not implemented in streaming mode. Please use dl_manager.iter_archive instead.`
If the label files are present as .txt files then we can directly use dl_manager.download.




The rvl-cdip.tar.gz archive and txt files with the labels are on the Hub!

- Added 🤗 Hub download links.
- streamable and non-streamable versions of _generate_examples.
- Updated dummy data, both real and dummy dataset tests have passed.



I've removed the extraction of the archive file locally as suggested. Let me know if any other changes are required. :)

The check for **Update Hub repositories / update-hub-repositories** has failed.

> https://github.com/huggingface/datasets/runs/6116502392?check_suite_focus=true



Hi ! Thanks for reporting ;) yes this CI job has been failing for a few days. I'm working on fixing it, and I'm manually running it on my side in the meantime

Great. :D Thank you @lhoestq