separating the geojson sources for the route line and casing line for …

[cafesilencio]

Description

There was a bug on the maps side that resulted in the route line casing not appearing. See https://github.com/mapbox/mapbox-gl-native-internal/issues/268

As a work around for a maps issue not drawing the casing for the route line when they share the same geoJson source, this PR creates separate sources so the the casing line will appear.

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[LukasPaczos]

@cafesilencio whenever you can, could go ahead and revert this change on master? 😁 We are depending on the Maps SDK 9.4.x now, so we shouldn't need this workaround anymore.