### 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)

airflow/providers/databricks/hooks/databricks.py
"""
        Function to get AAD token for given resource. Supports managed identity or service principal auth
        :param resource: resource to issue token to
        :return: AAD token, or raise an exception
        """
        if resource in self.aad_tokens:
            d = self.aad_tokens[resource]
            now = int(time.time())
            if d['expires_on'] > (now - TOKEN_REFRESH_LEAD_TIME):  
                return d['token']
            self.log.info("Existing AAD token is expired, or going to expire soon. Refreshing...")
        attempt_num = 1
        while True:
            try:
                if self.databricks_conn.extra_dejson.get('use_azure_managed_identity', False):
                    params = {
                        "api-version": "2018-02-01",
                        "resource": resource,
                    }
                    resp = requests.get(
                        AZURE_METADATA_SERVICE_TOKEN_URL,
                        params=params,
                        headers={**USER_AGENT_HEADER, "Metadata": "true"},
                        timeout=self.aad_timeout_seconds,
                    )
                else:
                    tenant_id = self.databricks_conn.extra_dejson['azure_tenant_id']
                    data = {
                        "grant_type": "client_credentials",
                        "client_id": self.databricks_conn.login,