Process maxspeed tag before surface, smoothness, and tracktype tags (#6002)

* Handle maxspeed tags before surface and smoothness tags

Let's say we have a tertiary road with the following tags:

   highway=tertiary
   maxspeed=60
   surface=gravel
   smoothness=intermediate

While the maxspeed tag tells us the legal speed limit, the surface and
smoothness tags have much more effect on the real-world speed of a car.
We should process the maxspeed tags first, and then update the road's
forwards/backwards speeds according to any surface and smoothness tags.
For our hypothetical road the process in the car.lua profile now goes
like this:

1. Get default speed from profile (tertiary = 40 on line 150 of car.lua)
2. Change speed to 60 using maxspeed tag (WayHandlers.maxspeed function
   in way_handlers.lua, lines 434-447)
3. Change speed to 40 using surface tag (WayHandlers.surface function
   in way_handlers.lua, lines 360-363)
4. Check speed according to smoothness tag --- but because it's higher
   than the speed according to the surface tag, leave the speed
   unchanged (WayHandlers.surface function again, lines 368-371)

<https://github.com/Project-OSRM/osrm-backend/blob/ec36319232f6b6558080c5586d21fc0bd150de44/profiles/car.lua#L150>
<https://github.com/Project-OSRM/osrm-backend/blob/ec36319232f6b6558080c5586d21fc0bd150de44/profiles/lib/way_handlers.lua#L354-L372>

Note in step 3 above the speed's only changed from 60kph to 40kph
because it's a lower value. If the surface speed was higher than than
the previous value, the speed would remain unchanged. Another example:

   highway=tertiary
   maxspeed=60
   surface=compacted
   smoothness=intermediate

Here, although the profile's speed for compacted is 80, it would stay at
the lower value of 60 (see way_handlers.lua, lines 360-363).

<https://github.com/Project-OSRM/osrm-backend/blob/ec36319232f6b6558080c5586d21fc0bd150de44/profiles/lib/way_handlers.lua#L360-L363>

Author: flother

profiles/car.lua

@@ -432,8 +432,8 @@ function process_way(profile, way, result, relations)
 
     -- compute speed taking into account way type, maxspeed tags, etc.
     WayHandlers.speed,
-    WayHandlers.surface,
     WayHandlers.maxspeed,
+    WayHandlers.surface,
     WayHandlers.penalties,
 
     -- compute class labels