Add a files suffix to file paths in S3

[imsdu]

Motivation
In #4924, we will introduce file sets which will be a distinct entity, it would be valuable to easily make the difference between them at the project level in the S3 bucket.

Having a clear distinction between them will help to use tools like AWS S3 Inventory

Acceptance criteria

1. The file prefix was /[prefix]/[org]/[project]/[uuid]/[filename] and will now be /[prefix]/[org]/[project]/files/[uuid]/[filename]