toSerializable omits link columns

[kostasb]

Describe the bug
Calling toSerializable on a record omits linked columns.

Repro steps
Reproduced with client 0.26.5:

const results = await xata.db.one.select(["*", "mylink.*"]).getAll();

for (const res of results) {
  const res_ser = res.toSerializable();
  console.log(res);
  console.log(res_ser);
}

Results:

// record:
{
  "id": "rec_ck20o0j004smhor4oh9g",
  "mylink": {
    "id": "rec_ck20nusmtttmmmr6kgag",
    "linkedstring": "two",
  },
  "mystring": "one",
}

// serialized record is missing mylink.linkedstring:
{
  "id": "rec_ck20o0j004smhor4oh9g",
  "mylink": "rec_ck20nusmtttmmmr6kgag",
  "mystring": "one"
}