Make `angleToNextSegment` reporting consistent

The issue concerns the tool named SegmentsInfoExtractor (https://gitlab.com/ssv/AnalysisSitus/-/blob/master/src/asiAlgo/auxiliary/asiAlgo_SegmentsInfoExtractor.h?ref_type=heads). This tool has been employed by our SDK users to estimate cutting times for flat parts (sheet metal being the primary use case).

It was discovered that sometimes the angles reported for consecutive segments look strange: a smooth connection can get either 0 or 180 degrees. This inconsistency makes it impossible to analyze smooth joints over a contour, because the angle convention is not agreed upon and therefore not respected. Here are some guidelines for possible fixes:

• It might make sense to reuse the "vertex vexity" checker that is based on the local neighborhood analysis and does not depend on parameterization directions of the edges' curves. See also https://analysissitus.org/features/features_check-vertex-vexity.html.
• For such analysis to become possible, it is essential to have the enclosed material, i.e. the contour being analyzed should be checked in the context of a face it's attached to. If there's no such face (e.g., this is the case for DXF drawings), then an artificial one has to be constructed and used all over the contour's edges to keep the angles consistent.
• The extracted values need to get coverage in the unit tests.
• The documentation pages need to be updated (this mainly concerns the "extensions" product pages).