feat(kubernetes_events source): add k8s events src

[elohmeier]

Summary

This PR adds a new kubernetes_events source that watches the Kubernetes Events API and emits each event as a Vector log event. This addresses a long-standing feature request and brings Vector closer to feature parity with other observability tools in the Kubernetes ecosystem.

The design is influenced by similar implementations in:

• https://docs.fluentbit.io/manual/pipeline/inputs/kubernetes-events
• https://github.com/resmoio/kubernetes-event-exporter

Key features:

• Watches the modern events.k8s.io/v1 API (not the deprecated core/v1 Event API)
• Supports namespace filtering, field selectors, and label selectors
• Filters by event type (Warning, Normal), reason, and involved object kind
• Built-in deduplication to handle Kubernetes event replay on API reconnection
• Configurable max event age to skip stale events on startup
• Optional inclusion of previous event state for change tracking
• Designed for singleton deployment (one instance per cluster)

We've been using this in Production in various clusters for some weeks now and it has been working fine.

Vector configuration

sources:
  k8s_events:
    type: kubernetes_events
    namespaces:
      - kube-system
      - default
    include_types:
      - Warning
    max_event_age_seconds: 3600

sinks:
  console:
    type: console
    inputs:
      - k8s_events
    encoding:
      codec: json

How did you test this PR?

• Unit tests for deduplication logic, event timestamping, and filtering
• Manual testing against a local Kubernetes cluster (kind/minikube)
• Verified event streaming, reconnection handling, and deduplication behavior

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Closes: New kubernetes_system_events source #1293

[maycmlee]

Just some small suggestions!