use jq schema for content_key in json_loader
Labels: name: area: doc loader, name: auto:improvement

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### Description
Changed the value specified for `content_key` in JSONLoader from a single key to a value based on jq schema.

Sorry, I created the [same Pull Request](https://github.com/langchain-ai/langchain/pull/8075) in the past, but some time has elapsed and it was closed, so I am recreating it.

### Why
For json data like the following, specify `.data[].attributes.message` for page_content and `.data[].attributes.id` or `.data[].attributes.attributes. tags`, etc., the `content_key` must also parse the json structure.

<details>
<summary>sample json data</summary>

```json
{
  "data": [
    {
      "attributes": {
        "attributes": {
          "dd": {
            "service": "worker",
            "env": "production",
            "version": "6b2c46a5883a9097aa2cb09907786b5c06ca3bd0"
          },
          "source": "stderr",
          "service": "worker",
          "name": "app.services.predict_services",
          "levelname": "ERROR",
          "container_id": "f9f880b243cc41f1a7d9bae5bf922d60-1262558729",
          "timestamp": 1686679407827.0
        },
        "message": "error while processing user #19084: 'numpy.dtype[bool_]' object is not callable",
        "service": "worker",
        "status": "error",
        "tags": [
          "datadog.submission_auth:private_api_key",
          "env:production"
        ],
        "timestamp": "2023-06-14T03:03:27.827000+09:00"
      },
      "id": "AgAAAYi17UzTUeIczgAAAAAAAAAYAAAAAEFZaTE3VThXQUFEOF9sS2J4Z3psRmdBRAAAACQAAAAAMDE4OGI2MzYtMmZlNC00ZDEwLThjZDMtMzhkZTI0NmUyNWMz",
      "type": "log"
    },
    {
      "attributes": {
        "attributes": {
          "dd": {
            "service": "worker",
            "env": "production",
            "version": "6b2c46a5883a9097aa2cb09907786b5c06ca3bd0"
          },
          "process": 42.0,
          "messages": "error while processing user #19084: 'numpy.dtype[bool_]' object is not callable",
          "levelname": "ERROR",
          "container_id": "f9f880b243cc41f1a7d9bae5bf922d60-1262558729",
          "timestamp": 1686679407831.0
        },
        "message": "{\"messages\": \"error while processing user #19084: 'numpy.dtype[bool_]' object is not callable\"}",
        "service": "worker",
        "status": "error",
        "tags": [
          "datadog.submission_auth:private_api_key",
          "env:production"
        ],
        "timestamp": "2023-06-14T03:03:27.831000+09:00"
      },
      "id": "AgAAAYi17UzXUeIczwAAAAAAAAAYAAAAAEFZaTE3VThXQUFEOF9sS2J4Z3psRmdBRQAAACQAAAAAMDE4OGI2MzYtMmZlNC00ZDEwLThjZDMtMzhkZTI0NmUyNWMz",
      "type": "log"
    }
  ],
  "meta": {
    "elapsed": 26,
    "request_id": "pddv1ChY0SmttaDA0a1REeXZRM01yNkFwYnd3Ii0KHWIANr8mghGpsMIX2cOarI6t4WyTVObXx3wrAuudEgzSbtmduLtPxFVkSo0",
    "status": "done"
  }
}

```

</details>

<details>
<summary>sample code</summary>

```python
def metadata_func(record: dict, metadata: dict) -> dict:
    print(record)

    metadata["id"] = record.get("id")
    metadata["tags"] = record["attributes"].get("tags")

    return metadata

sample_file = "sample.json"
loader = JSONLoader(
    file_path=sample_file,
    jq_schema=".data[]",
    content_key=".attributes.message",
    metadata_func=metadata_func
)
```

</details>

### Dependencies
none

### Tag maintainer
@rlancemartin, @eyurtsev

### Twitter handle
[kzk_maeda](https://twitter.com/kzk_maeda)