Fixes bugs where UV islands with `mark seam` would tear at boundaries.
Modify seam_connected to search both it's edges instead of only one,
as this could fail if the edge was a seam or did not fan to the other loop.
Also fixes bug in `seam_connected_recursive`:
- `loop->prev == needle` changed to `loop == needle`
Maniphest Tasks: T103787
Reviewed By: Campbell Barton
Differential Revision: https://developer.blender.org/D16992
Test File: F14145477, F14137755, T79304
4160da187c