Due to some rather complex logic that tries to calculate intersection
angles by looking further up the road, it's possible to return
an intersection view that is missing a u-turn - something which
is assumed to exist in later guidance calculations.
We apply a fix here by ensuring the u-turn is always included in
the returned view.
Currently OSRM only supports turn restrictions with a single via-node or one
via-way. OSM allows for multiple via-ways to represent longer and more
complex restrictions.
This PR extends the use of duplicate nodes for representng via-way turn
restrictions to also support multi via-way restrictions. Effectively, this
increases the edge-based graph size by the number of edges in multi via-way
restrictions. However, given the low number of these restrictions it
has little effect on total graph size.
In addition, we add a new step in the extraction phase that constructs
a restriction graph to support more complex relationships between restrictions,
such as nested restrictions and overlapping restrictions.
