Add singleshell benchmarking recon workflow

[tsalo]

Summary

Copying over the info from @mattcieslak's QSIPrep PR (PennLINC/qsiprep#780).

cc @ameliecr

We're working on a project to compare tractometry methods using different reconstruction methods on single-shell acquisitions. There are too many initial steps that need to be shared for autotrack to use the simple recon spec json format. So this workflow would break up the initial calculation of qa and iso, and registration into separate steps.

Relevant thread: https://groups.google.com/g/dsi-studio/c/emMz-K8ewlo