Extract common logic for S3

[antonio2368]

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Extending S3-related functions/classes became a bit hard with everything in a huge S3Common.cpp file.
I split the logic from there into different files (most of them are credentials related).
Also, I noticed that we didn't modify the logic for parsing args for S3 storage, just for the table functions. I extracted the logic for argument parsing so we don't make the same mistake again.

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