This problem occurs because of obtaining 2 ALines which share same vertex on the seam edge.
There should be 2 different vertices with same(or almost the same) 3d parameters, but
with different UV parameters because of periodic surface.
Current fix allows to avoid the same vertices on seam edge and also checks the next vertex.
1. Modify method IntPatch_ALineToWLine::MakeWLine: add correction of end points of each line on 2 surfaces if an end point is a pole on a surface.
2. Modify method IntPatch_WLine::ComputeVertexParameters: adjust a point on curve to corresponding vertex the following way: set 3D point as the point of the vertex and 2D points as the points of the point on curve.
1. New testgrid "lowalgos/intss" has been created. It will contain all test cases on geometrical intersection of two surfaces ("intersect" DRAW-command) and two faces ("bopcurves" DRAW-command).
2. New test case for the issue #28493 has been created because the problem is not reproduced on MASTER.
3. Test case (lowalgos/intss/bug24472) for the issue #29501 has been modified in order to check loops of the resulting intersection curves.
