Support for name:left, name:right

[lonvia]

There are streets along borders that have a different name on the right and left side of the road. OSM uses name:left and name:right for these streets. Example in Italy:

https://www.openstreetmap.org/way/78592609

This may also happen on country boundaries, where the road would even need to get assigned into two different partitions.

Nominatim should show the correct street for addresses along such roads. Currently only the name is shown (which normally has both names).

(Original report in #785)