[P0] event-exporter: migrate watcher to events.k8s.io/v1 to reduce event churn

[erain]

Problem

event-exporter watches core/v1 Events. These objects are updated frequently (count/lastTimestamp), generating high update volume and write amplification to Cloud Logging under heavy load. This increases CPU, memory, and egress in large clusters.

Proposed optimization

Switch the event watcher to events.k8s.io/v1 and map EventSeries to reduce update frequency. In the newer Events API, repeated events are represented as a series (series.count, series.lastObservedTime) rather than continuous updates to a single core/v1 Event. This should significantly reduce update traffic and improve throughput in high-volume clusters.

Notes / references

• Events API group: https://kubernetes.io/docs/reference/kubernetes-api/cluster-resources/event-v1/
• EventSeries semantics: https://kubernetes.io/docs/reference/kubernetes-api/cluster-resources/event-v1/#EventSeries
• client-go typed client: k8s.io/client-go/kubernetes/typed/events/v1

Acceptance criteria

• Watcher uses events.k8s.io/v1 client and handles EventSeries semantics.
• Observed reduction in update volume vs. core/v1 (documented via metrics or basic benchmarking).
• Backward-compatible behavior for log entry fields used by sink (no loss of required data).