Optionally use addr:street values as autocomplete data for name tags

[rasher]

It would be nice if the available data in addr:street tags was available as autocomplete data when entering a name tag. This would be useful especially in Denmark, where we have a full import of address points (and other areas with similar data). This way, when entering the name of a street, it would already be in the autocomplete list. Perhaps this should only be done for ways with a highway=* tag.

I understand this would be somewhat unexpected behaviour, so it would probably be best off as a setting (hidden or not).

This would be very helpful when mapping streets in Denmark and other areas with address data but missing streets.

[stoecker]

Closed as duplicate of #6306.