Cilium leader fails hook "send-remote-write-relation-joined" due to missing .kube/config

(related to LP: #2025157)

When deploying cilium related to cos-prometheus the installation fails with hook `failed: "send-remote-write-relation-joined"`:

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Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/config/kubeconfig.py", line 175, in from_service_account
    token = account_dir.joinpath("token").read_text()
  File "/usr/lib/python3.10/pathlib.py", line 1134, in read_text
    with self.open(mode='r', encoding=encoding, errors=errors) as f:
  File "/usr/lib/python3.10/pathlib.py", line 1119, in open
    return self._accessor.open(self, mode, buffering, encoding, errors,
FileNotFoundError: [Errno 2] No such file or directory: '/var/run/secrets/kubernetes.io/serviceaccount/token'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/config/kubeconfig.py", line 210, in from_env
    return KubeConfig.from_service_account(service_account=service_account)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/config/kubeconfig.py", line 178, in from_service_account
    raise exceptions.ConfigError(str(e))
lightkube.core.exceptions.ConfigError: [Errno 2] No such file or directory: '/var/run/secrets/kubernetes.io/serviceaccount/token'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-cilium-0/charm/./src/charm.py", line 336, in <module>
    main(CiliumCharm)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/main.py", line 441, in main
    _emit_charm_event(charm, dispatcher.event_name)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/main.py", line 149, in _emit_charm_event
    event_to_emit.emit(*args, **kwargs)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 354, in emit
    framework._emit(event)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 830, in _emit
    self._reemit(event_path)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 919, in _reemit
    custom_handler(event)
  File "/var/lib/juju/agents/unit-cilium-0/charm/lib/charms/prometheus_k8s/v0/prometheus_remote_write.py", line 673, in _handle_endpoints_changed
    self.on.endpoints_changed.emit(relation_id=event.relation.id)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 354, in emit
    framework._emit(event)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 830, in _emit
    self._reemit(event_path)
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/ops/framework.py", line 919, in _reemit
    custom_handler(event)
  File "/var/lib/juju/agents/unit-cilium-0/charm/./src/charm.py", line 266, in _on_remote_write_changed
    self._deploy_grafana_agent(self.remote_write_consumer.endpoints)
  File "/var/lib/juju/agents/unit-cilium-0/charm/./src/charm.py", line 172, in _deploy_grafana_agent
    self._client.apply(obj)
  File "/usr/lib/python3.10/functools.py", line 981, in __get__
    val = self.func(instance)
  File "/var/lib/juju/agents/unit-cilium-0/charm/./src/charm.py", line 101, in _client
    client = Client(field_manager=f"{self.model.app.name}")
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/core/client.py", line 43, in __init__
    self._client = GenericSyncClient(config, namespace=namespace, timeout=timeout, lazy=lazy,
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/core/generic_client.py", line 82, in __init__
    config = KubeConfig.from_env().get()
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/config/kubeconfig.py", line 212, in from_env
    return KubeConfig.from_file(os.environ.get('KUBECONFIG', default_config))
  File "/var/lib/juju/agents/unit-cilium-0/charm/venv/lightkube/config/kubeconfig.py", line 142, in from_file
    raise exceptions.ConfigError(f"Configuration file {fname} not found")
lightkube.core.exceptions.ConfigError: Configuration file ~/.kube/config not found
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The error message is very descriptive, but the preferred behaviour would be to retry the hook later when the kube/config is synchronized.