limited anchors, while before a full perimeter segment was always
taken if possible.
2) Adapted the line infills (grid, stars, triangles, cubic) to 1).
This also solves a long standing issue of these infills producing
anchors for each sweep direction independently, thus possibly
overlapping and overextruding, which was quite detrimental
in narrow areas.
3) Refactored cubic adaptive infill anchroing algorithm
for performance and clarity.
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