**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
def setUp(self):
        self.watcher = KubernetesJobWatcher(
            namespace="airflow",
            multi_namespace_mode=False,
            watcher_queue=mock.MagicMock(),
            resource_version="0",
            scheduler_job_id="123",
            kube_config=mock.MagicMock(),
        )
        self.kube_client = mock.MagicMock()
        self.core_annotations = {
            "dag_id": "dag",
            "task_id": "task",
            "execution_date": "dt",
            "try_number": "1",
        }
        self.pod = k8s.V1Pod(
            metadata=k8s.V1ObjectMeta(
                name="foo",
                annotations={"airflow-worker": "bar", **self.core_annotations},
                namespace="airflow",
                resource_version="456",
            ),
            status=k8s.V1PodStatus(phase="Pending"),
        )
        self.events = []
    def _run(self):