Make edge weight a strongly defined type

[oxidase]

Working on #2399 found different weight types

• unsigned

  osrm-backend/include/contractor/contractor_graph.hpp

  Line 29 in a5d0707

  unsigned weight;

• std::int32_t

  osrm-backend/src/engine/routing_algorithms/routing_base.cpp

  Line 23 in a5d0707

  const std::int32_t weight = forward_heap.GetKey(node);

• int

  osrm-backend/src/engine/routing_algorithms/many_to_many.cpp

  Line 131 in a5d0707

  const int source_weight = query_heap.GetKey(node);

PR #2399 unifies weight types as EdgeWeight but compile-time type checking is required to check all places.
It would also good to define strongly typed EdgeDuration, TurnWeight and TurnDuration to have compile-type checks and avoid problems by mixing edge/turn weights and durations.

[daniel-j-h]

Yes, yes please. I poked @danpat often enough some time ago that we ended up building and incorporating

https://github.com/Project-OSRM/osrm-backend/blob/master/include/util/strong_typedef.hpp#L43
https://github.com/Project-OSRM/osrm-backend/blob/master/include/util/typedefs.hpp#L40-L44

which is similar to the one in Boost, except that it does not allow implicit conversions.

[danpat]

@oxidase yeah, you want to take a look and see if OSRM_STRONG_TYPEDEF is usable here? Check the OSMNodeID type as an example (also, include/util/coordinate.hpp where we use it to prevent lon/lat swap mistakes).

It should be fully optimized away under -O3, and will give the compile-time checking you're after.

[TheMarex]

This has no clear priority right now. We should have a look at this when we got some downtime for refactors.