Polish EIC data files

[comane]

This PR aims at polishing the ATHENA data files.
Things that are done:

• moved all xlsx files into a rawdata folder
• added openpyxl to poetry extras. This is needed by pd.read_excel
• created an athena_utils.py file so as to minimise repeated code.

[comane]

@scarlehoff @Radonirinaunimi @RoyStegeman I think we should probably have a nnpdf_data/filter_utils folder that contains all filter utils modules for datasets. What do you think

[RoyStegeman]

Thanks, I'll have a closer look later, but I agree that, if it makes sense to have multiple filter utils with e.g. some corresponding to only a single experiment, it would be good to have a filter_utils folder. That's exactly the sort of thing that's needed

[Radonirinaunimi]

Thanks so much for this @comane!

@scarlehoff @Radonirinaunimi @RoyStegeman I think we should probably have a nnpdf_data/filter_utils folder that contains all filter utils modules for datasets. What do you think

Yes, something along that line should definitely be adopted, and as a matter of fact I was planning to discuss with you (later this week) about the main utils that were/are required in the datasets you implemented in order to draft something.

In this respect, as far as this PR is concerned, you could already move athena_ultis.py in a folder nnpdf_data/filter_utils.

[Radonirinaunimi]

@comane, @RoyStegeman, given that these Athena share quite a lot of the functions with the other EIC projections, I also fixed them here. I therefore renamed the module from athena_utils $\longrightarrow$ eic_utils.

[RoyStegeman]

Please rebase so the tests will pass

[RoyStegeman]

Thanks, seems fine to me

[Radonirinaunimi]

@comane I think this is done now, please merge if you are fine with this.

[comane]

thanks @Radonirinaunimi and @RoyStegeman for reviewing!

[RoyStegeman]

You only force-pushed your local changes. I still have the commits from the review locally, would you like me to push those?

[comane]

Yes please, I might have done a mess.
I had rebased on master but perhaps I didn't pull from the branch :(