**Apache Airflow version**: 2.0.1


**Kubernetes version (if you are using kubernetes)** (use `kubectl version`): 1.20.5

**Environment**:

- **Cloud provider or hardware configuration**: Azure AKS

**What happened**:

When task or dag name is defined with a non ascii character, pod creations fails with a kubernetes.client.rest.ApiException: (422)
(task maintains scheduled status)
this is because the hostname defined for the pod is based on dag and task name...

**What you expected to happen**:

Create the pod and run the task

**How to reproduce it**:
Run a task with name "campaña" on K8s executor,

Error log
```
{"kind":"Status","apiVersion":"v1","metadata":{},"status":"Failure","message":"Pod \"dagnamecampaña.0fb696e661e347968216df454b41b56f\" is invalid: metadata.name: Invalid value: \"dagnamecampaña.0fb696e661e347968216df454b41b56f\": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0
-9])?(\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')","reason":"Invalid"
```



tests/executors/test_kubernetes_executor.py
current_folder = pathlib.Path(__file__).parent.absolute()
        template_file = str(
            (current_folder / "kubernetes_executor_template_files" / "basic_template.yaml").absolute()
        )
        mock_kube_client = mock.patch('kubernetes.client.CoreV1Api', autospec=True)
        mock_get_kube_client.return_value = mock_kube_client
        with conf_vars({('kubernetes', 'pod_template_file'): ''}):
            executor = self.kubernetes_executor
            executor.start()
            assert executor.event_buffer == {}
            assert executor.task_queue.empty()
            execution_date = datetime.utcnow()
            executor.execute_async(
                key=('dag', 'task', execution_date, 1),
                queue=None,
                command=['airflow', 'tasks', 'run', 'true', 'some_parameter'],