### Apache Airflow Provider(s)

databricks

### Versions of Apache Airflow Providers

apache-airflow-providers-databricks==1!2.0.2


### Apache Airflow version

2.1.4 (latest released)

### Operating System

Debian GNU/Linux 11 (bullseye)

### Deployment

Docker-Compose

### Deployment details

Running local deployment using Astronomer CLI

### What happened

When calling the `get_run_state` method from the `DatabricksHook`, I get the following error:

`TypeError: Object of type RunState is not JSON serializable`

I think this is due to [the method returning a RunState custom class](https://github.com/apache/airflow/blob/main/airflow/providers/databricks/hooks/databricks.py#L275) as opposed to a `str` like the rest of the methods in the databricks hook (i.e. `get_job_id`, `get_run_page_url`, etc.)

### What you expected to happen

When calling the `get_run_state` method, simply return the `result_state` or `state_message` [variables](https://github.com/apache/airflow/blob/main/airflow/providers/databricks/hooks/databricks.py#L287-L288) instead of the `RunState` class.

### How to reproduce

Create a dag that references a databricks deployment and use this task to see the error:

```
    from airflow.providers.databricks.hooks.databricks import DatabricksHook
    run_id = <insert run id from databricks ui here>

    def get_run_state(self, run_id: str):
           return self.hook.get_run_state(run_id=run_id)

    python_get_run_state = PythonOperator(
        task_id="python_get_run_state",
        python_callable=get_run_state,
        op_kwargs={
            "run_id": str(run_id)
        }
    )
```

### Anything else

_No response_

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

tests/providers/databricks/hooks/test_databricks.py
"""
    Utility function to generate the install endpoint given the host.
    """
    return f'https://{host}/api/2.0/libraries/install'
def uninstall_endpoint(host):
    """
    Utility function to generate the uninstall endpoint given the host.
    """
    return f'https://{host}/api/2.0/libraries/uninstall'
def create_valid_response_mock(content):
    response = mock.MagicMock()
    response.json.return_value = content
    return response
def create_successful_response_mock(content):
    response = mock.MagicMock()
    response.json.return_value = content
    response.status_code = 200
    return response
def create_post_side_effect(exception, status_code=500):
    if exception != requests_exceptions.HTTPError:
        return exception()
    else:
        response = mock.MagicMock()
        response.status_code = status_code
        response.raise_for_status.side_effect = exception(response=response)
        return response
def setup_mock_requests(mock_requests, exception, status_code=500, error_count=None, response_content=None):