**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"
```



airflow/kubernetes/kubernetes_helper_functions.py
"""
    Generates the kubernetes safe pod_id. Note that this is
    NOT the full ID that will be launched to k8s. We will add a uuid
    to ensure uniqueness.
    :param dag_id: DAG ID
    :param task_id: Task ID
    :return: The non-unique pod_id for this task/DAG pairing
    """
    safe_dag_id = _strip_unsafe_kubernetes_special_chars(dag_id)
    safe_task_id = _strip_unsafe_kubernetes_special_chars(task_id)
    return safe_dag_id + safe_task_id
def annotations_to_key(annotations: Dict[str, str]) -> Optional[TaskInstanceKey]:
    """Build a TaskInstanceKey based on pod annotations"""
    log.debug("Creating task key for annotations %s", annotations)
    dag_id = annotations['dag_id']
    task_id = annotations['task_id']
    try_number = int(annotations['try_number'])
    execution_date = parser.parse(annotations['execution_date'])
    return TaskInstanceKey(dag_id, task_id, execution_date, try_number)