TrafficArea streams now don't stop early and support RoadRanges with more than 2 cursors

AppendCrossRoad now calculates the fence-post finalization differently when the stream only has 1 lane and when it has multiple.

Changed CreateTrafficArea, and changed and renamed Append to BuildStreams (because it now does more than just append), so that:

• Whenever a stream can't append, it now stores the failed stream and keeps appending the rest;
• Whenever a RoadCursor is defined but its road's lanes are not all already contained in a stream, new streams are created for the missing lanes.

These changes make the TrafficAction documentation example at https://publications.pages.asam.net/standards/ASAM_OpenSCENARIO/ASAM_OpenSCENARIO_XML/v1.4.0/07_components_scenario/07_04_actions.html#_global_action work.