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.