[Networking] Geneve tunnel conncheck

[cheina97]

Summary

This PR adds an active connectivity health-check (ping) mechanism for Geneve tunnels, tracking connection status and latency directly on the GeneveTunnel CRD.

What changed:

• GeneveTunnel CRD extended — added a Status subresource with value (Connected/Error) and latency fields, plus kubectl get print columns for quick status inspection.
• Gateway InternalNodeReconciler — on reconcile, lazily initialises a ConnChecker bound to the gateway's inner Geneve IP; registers a UDP ping sender per tunnel and wires a callback that writes connectivity results back to GeneveTunnel status. Senders are stopped when the corresponding InternalNode is deleted.
• Fabric InternalFabricReconciler — lazily starts a ConnChecker receiver bound to the node's inner Geneve IP, so the fabric side can respond to pings from the gateway.
• ConnChecker improvements:
  • Supports binding to a specific IP (BindIP option), enabling per-interface isolation between Geneve and WireGuard ping traffic.
  • Latency is now smoothed with an EWMA (PingLatencyAlpha option, default 0.1) instead of using raw per-packet measurements.
• New flags (gateway geneve-fabric component):
  • --geneve-ping-enabled (default true)
  • --geneve-ping-port (default 12346)
  • --geneve-ping-interval (default 2s)
  • --geneve-ping-loss-threshold (default 5)
  • --geneve-ping-update-status-interval (default 10s)
  • --geneve-ping-latency-alpha (default 0.1)
• New flag (fabric component): --geneve-ping-port must match the gateway value.
• New flag (connection component): --ping-latency-alpha applies the same EWMA smoothing to WireGuard connection checks.

How it works

Gateway InternalNodeReconciler
  └─ ConnChecker (sender, bound to gateway inner IP)
       └─ UDP ping → Fabric node inner IP : geneve-ping-port
            └─ ConnChecker (receiver, bound to node inner IP)
       └─ pong → callback → GeneveTunnel.Status.{Value, Latency}

When --geneve-ping-enabled=false the status is set to Connected immediately without running the ping loop.

Test plan

• Deploy two clusters peered with Geneve mode.
• Verify kubectl get genevetunnels shows Connected and a latency value after a few seconds.
• Delete an InternalNode; verify no goroutine leak (sender is stopped).
• Test with --geneve-ping-enabled=false; verify status is immediately Connected.

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[cheina97]

/build