**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
executor = self.kubernetes_executor
        executor.start()
        key = ('dag_id', 'task_id', 'ex_time', 'try_number1')
        executor._change_state(key, State.RUNNING, 'pod_id', 'default')
        assert executor.event_buffer[key][0] == State.RUNNING
    @mock.patch('airflow.executors.kubernetes_executor.KubernetesJobWatcher')
    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
    @mock.patch('airflow.executors.kubernetes_executor.AirflowKubernetesScheduler.delete_pod')
    def test_change_state_success(self, mock_delete_pod, mock_get_kube_client, mock_kubernetes_job_watcher):
        executor = self.kubernetes_executor
        executor.start()
        test_time = timezone.utcnow()
        key = ('dag_id', 'task_id', test_time, 'try_number2')
        executor._change_state(key, State.SUCCESS, 'pod_id', 'default')
        assert executor.event_buffer[key][0] == State.SUCCESS
        mock_delete_pod.assert_called_once_with('pod_id', 'default')
    @mock.patch('airflow.executors.kubernetes_executor.KubernetesJobWatcher')
    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
    @mock.patch('airflow.executors.kubernetes_executor.AirflowKubernetesScheduler.delete_pod')
    def test_change_state_failed_no_deletion(