The internal representation of turn restrictions expects only one
`from` way and only one `to` way.
`no_entry` and `no_exit` turn restrictions can have multiple `from` and
`to` ways respectively. This means they are not fully supported by
OSRM's restriction parser.
We complete support for these turn restriction types by parsing all
ways and converting a valid restriction with multiple `from`/`to` members
into multiple internal restrictions.
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.
