DEV: improved optimization pipeline for straightening
DEV: improved optimization pipeline for straightening

Former-commit-id: be3545353bca2e40925c213966dcb4489e513a69
Former-commit-id: 026d0a8cab829929d6e69670f33c31beb84a3890
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox