Generalize wikidata field

[tyrasd]

from openstreetmap/id-tagging-schema#769 (comment):

I think we should think about a better solution, e.g. involving an improved "wikidata" field which can directly work on a tag-triplet, e.g. operator + operator:wikidata + operator:wikipedia.

A possible definition:

{
    "key": "operator",
    "keys": [
        "operator:wikidata",
        "operator:wikipedia"
    ],
    "type": "text+wikidata",
    "label": "Operator"
}

see also openstreetmap/id-tagging-schema#168

[1ec5]

This is related to the idea of grouping semantically related fields together: openstreetmap/iD#8104. The advantage to special-casing the Wikidata/Wikipedia triplet, as opposed to a more general solution, is that iD can more confidently unlock such a field. The reason for locking them in the first place was the risk that the individual tags would get out of sync.