Introduce locationSet.unsearchable to hide presets for regions but not disable them

[tordans]

The way I read locationSet is, that those presets are fully hidden when mapping in that region, so no matching takes place at all.
(Is that correct?)

But what if I want to hide some presets automatically in certain regions (like searchable:false does) and not "remove" them from the local preset list?

Such a feature would allow us handle cases like https://wiki.openstreetmap.org/wiki/DE:Tag:traffic_sign%3DDE:240 where highway=path/cycleway are suggested with only slight preference for path. In this example, both taggings exist and are valid but only one should be suggested by the id-tagging-schema with the other one still visible like an un-searchable preset.

See also openstreetmap/id-tagging-schema#1205