Check that fields are quoted correctly if they are named after
the matchN builtin.

-- schema.json --
{
    "type": "object",
    "properties": {
        "matchN": {
            "oneOf": [
                {
                    "const": 1
                },
                {
                    "const": 2
                }
            ]
        }
    }
}
-- out/decode/extract --
"matchN"?: matchN(1, [1, 2])
...
-- test/ok1.json --
{"matchN": 1}
-- test/ok2.json --
{"matchN": 2}
-- test/err-nomatch.json --
{"matchN": 3}
-- out/decode/testerr/err-nomatch --
matchN: conflicting values 1 and 3:
    generated.cue:1:23
    test/err-nomatch.json:1:12
matchN: conflicting values 2 and 3:
    generated.cue:1:26
    test/err-nomatch.json:1:12
matchN: invalid value 3 (does not satisfy matchN): 0 matched, expected 1:
    generated.cue:1:12
    generated.cue:1:19
    test/err-nomatch.json:1:12
