Implement "allow 3d arcs" for arc fitting

[evilDave]

Is your feature request related to a problem? Please describe.
Arc fitting does not operate when in spiral vase mode

Describe the solution you'd like
Add something similar to the code ArcWelderLib added (v1.0.1, see also FormerLurker/ArcWelderPlugin#56 (comment)) for allow-3d-arcs to the arc fitting code that is re-used here

I would be interested in looking into this, was just wondering if anyone else had started on anything.

[github-actions]

Orca bot: this issue is stale because it has been open for 90 days with no activity.

[github-actions]

Orca bot: This issue was closed because it has been inactive for 7 days since being marked as stale.