[Public transport] Display basic route results on the map

[bbecquet]

Probably easier to review commit by commit

Description

Displays public transport route results on the map, for now with the basic style, i.e. without any distinction of step type, metro line color, etc.
As public transport result geoms are GeoJSON FeatureCollection (and not unique geometries like car/walking/bike), we clean and refactor some stuff to be able to manage all results in a generic way, independently of the routing mode:

• always convert result data to a FeatureCollection MapBox-GL data source, even where there is a single feature
• use turf/bbox to compute bbox for all kinds of data

Why

• Display a first iteration of public transport results
• Increase the genericity of how we manage geoms

[amatissart]

I understand that using setFeatureState is not practical to update multiple features.
But reloading the whole geoJson data seems to be significantly slower.

Maybe another solution could be to define a routeId property in the features, and update the layer style (to set the line-color rule dynamically) ?

[bbecquet]

Thanks for the suggestion! 👌
I did it with the second alternative, as it didn't require manipulating each feature independently, requires a lot less code, and we already did something similar for the pedestrian case.
Now it's generic and snappy :)

[bbecquet]

I added that for iso-functionnalilty, because otherwise there is a 300ms transition effect which wasn't in the current version. We can drop it later if we decide the transition is nice :)

[amatissart]

arf, I was about to approve the PR, but the test needs to be updated too ;)