Logs of targetCluster Manager should be markred explicitly

[guettli]

/kind feature

When you see a log like this, you might think the caph process was shut down:

{"level":"INFO","time":"2025-04-24T11:43:14.773Z","file":"controller/controller.go:235","message":"Shutdown signal received, waiting for all workers to finish","controller":"certificatesigningrequest","controllerGroup":"certificates.k8s.io","controllerKind":"CertificateSigningRequest"}

But that is not the case. A cluster was deleted and the targetClusterManager was stopped.

Logs of the targetClusterManager should have a key-value pair which makes this more explicit, so that developers seeing logs from the targetClusterManager know where the logs coming from.