testing/fileshelter: upgrade to 6.2.0
https://github.com/epoupon/fileshelter/releases/tag/v6.2.0
https://github.com/epoupon/fileshelter/releases/tag/v6.1.0
https://github.com/epoupon/fileshelter/releases/tag/v6.0.0
Also fix a build error by including the algorithm header.