Add Karpenter integration via temporary PDBs

[xiangyuwang-stripe]

Summary

• Adds enableKarpenterIntegration feature flag to prevent Karpenter from disrupting Humio pods during upgrades and restarts
• When enabled, the operator creates a temporary PDB (maxUnavailable: 0) per node pool whenever the cluster is not fully stable, blocking all voluntary pod evictions
• PDBs are only removed after ensureMismatchedPodsAreDeleted confirms all pools have no diffs and the cluster is Running
• Feature is opt-in (default: false), existing users are unaffected

Background

The operator updates node pools one at a time, blocking pod creation for non-updating pools via nodePoolAllowsMaintenanceOperations. If Karpenter terminates a node in a healthy pool during another pool's upgrade, the lost pods cannot be recreated until the upgrade completes. This change prevents that by freezing Karpenter consolidation during sensitive operations.