Use more consistent terminology in projects admin UI

What does this MR do?

I was having trouble reconciling what I was seeing in GitLab Rails UI and what I was seeing in the praefect tooling. Having to translate between the two places makes it harder to understand how it fits together.

So I've harmonized the terminology in the UI with what you'll find in the documentation (both for GitLab Rails and for gitaly project). I've also made the description of the relative path much more verbose to help folks understand how it relates to the virtual storage.

• Before:

  

• After:

  

Author's checklist

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