[P1] event-exporter: reduce cache footprint with informer transform or minimal store

[erain]

Problem

Current watcher storage (DeltaFIFO/TTL) retains full event objects and fires handler callbacks for every add/update. Under heavy churn, this increases memory pressure and CPU overhead, especially when the sink only needs a subset of fields.

Proposed optimization

Use a SharedInformer with WithTransform to drop unused fields before objects are cached/processed, or implement a minimal store that retains only the fields needed for log entry creation. This reduces object size and avoids holding large event payloads in memory.

Notes / references

• SharedInformer WithTransform: https://pkg.go.dev/k8s.io/client-go/informers#WithTransform
• cache store implementations: https://pkg.go.dev/k8s.io/client-go/tools/cache

Acceptance criteria

• Event objects stored/queued contain only required fields for log entry creation.
• Memory usage under high event volume decreases vs. current storage.
• Functional behavior (log payloads) remains unchanged.