Alert when nodes fail to join cluster

[yulianedyalkova]

Related to https://github.com/giantswarm/adidas/issues/1325#issuecomment-2554383452

Tl;dr both Karpenter and cluster-autoscaler were trying to scale up but new nodes couldn't join the cluster because of issues with the bootstrap token (link). That resulted in continuous termination and recreation of the failing nodes.

We should be able to register this situation as early as possible instead of relying of unrelated alerts to catch the symptoms.