Add S3 storage and multi-hop transfer tutorial with resource files

[alessio94]

This PR supersedes #739 and addresses the feedback:

• Adds tutorial section on configuring S3 storage and multi-hop transfers
• Includes script files in hidden folder docs/operator/_resources/rucio-playground/ (as .txt since it was suggested that "the .sh could be rather nefarious looking")
• Removes external CERNBox link in favor of repo files
• Removes redundant "Rucio Documentation" link
  Thanks for the feedback
  @voetberg @rdimaio

[voetberg]

A few notes:

• I recommend not including that NB, it just means we need to update both the documentation page and the NB if there are changes.
• None of these scripts are anywhere close to too big to include inline - I think it's fine to just include them in the doc itself to make copy-pasting easier
• A lot of the comments on the scripts are not very descriptive, so it would be much easier to just describe them inline.
• Your method of just executing things directly in docker instead of entering an interactive session more difficult to follow than it needs to be. You can just assume the user already is within a rucio admin env if they're reading this as operator documentation
• This is also nominally about setting up s3 storage, not a from-scratch way to set up rucio, please don't include things like initializing environments