**Apache Airflow version**: 2.0.1
**Kubernetes version**: v1.19.7
**Executor**: KubernetesExecutor

**What happened**:

If you have a worker that gets stuck in pending forever, say with a missing volume mount, the task will stay in the queued state forever. Nothing is applying a timeout on it actually being able to start.

**What you expected to happen**:

Eventually the scheduler will notice that the worker hasn't progressed past pending after a given amount of time and will mark it as a failure.

**How to reproduce it**:
```python
from airflow import DAG
from airflow.operators.bash import BashOperator
from airflow.utils.dates import days_ago
from kubernetes.client import models as k8s


default_args = {
    "owner": "airflow",
}

with DAG(
    dag_id="pending",
    default_args=default_args,
    schedule_interval=None,
    start_date=days_ago(2),
) as dag:
    BashOperator(
        task_id="forever_pending",
        bash_command="date; sleep 30; date",
        executor_config={
            "pod_override": k8s.V1Pod(
                spec=k8s.V1PodSpec(
                    containers=[
                        k8s.V1Container(
                            name="base",
                            volume_mounts=[
                                k8s.V1VolumeMount(mount_path="/foo/", name="vol")
                            ],
                        )
                    ],
                    volumes=[
                        k8s.V1Volume(
                            name="vol",
                            persistent_volume_claim=k8s.V1PersistentVolumeClaimVolumeSource(
                                claim_name="missing"
                            ),
                        )
                    ],
                )
            ),
        },
    )
```


**Anything else we need to know**:
Related to:

* #15149 (This is reporting that these pending pods don't get deleted via "Mark Failed")
* #14556 (This handles when these pending pods get deleted and is already fixed)

airflow/executors/kubernetes_executor.py
self,
        pod_id: str,
        namespace: str,
        status: str,
        annotations: Dict[str, str],
        resource_version: str,
        event: Any,
    ) -> None:
        """Process status response"""
        if status == 'Pending':
            if event['type'] == 'DELETED':
                self.log.info('Event: Failed to start pod %s', pod_id)
                self.watcher_queue.put((pod_id, namespace, State.FAILED, annotations, resource_version))
            else:
                self.log.info('Event: %s Pending', pod_id)
        elif status == 'Failed':
            self.log.error('Event: %s Failed', pod_id)
            self.watcher_queue.put((pod_id, namespace, State.FAILED, annotations, resource_version))
        elif status == 'Succeeded':
            self.log.info('Event: %s Succeeded', pod_id)
            self.watcher_queue.put((pod_id, namespace, None, annotations, resource_version))
        elif status == 'Running':
            self.log.info('Event: %s is Running', pod_id)
        else:
            self.log.warning(
                'Event: Invalid state: %s on pod: %s in namespace %s with annotations: %s with '