NIFI-16120 Add caching for Kubernetes Leader Election Manager

[exceptionfactory]

Summary

NIFI-16120 Adds caching of current leader status for each role name to the KubernetesLeaderElectionManager using a delegated implementation class.

The caching strategy has a 5 second timeout, aligning with the approach in the ZooKeeper implementation. The cached leader status reduces repeated requests to the Kubernetes REST API when running large numbers of Processors on the Primary Node. The 5 second timeout is less than the current 15 second lease duration, and less than the 10 second renew deadline to avoid artificial extension of existing lease expiration.

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  • JDK 21
  • JDK 25

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[pvillard31]

LGTM, thanks @exceptionfactory