fix(controller): enable ARP learning on VPC routers that have peerings (#6882)

VPC peering requires ARP learning on the logical router. Cross-VPC traffic
arrives via the peer LRP, so the destination router needs to learn pod MACs
from ARP requests. Without it, packets are mis-forwarded (tunneled instead
of local delivery).

Previously, learnFromARPRequest was only set for EnableExternal and U2O
interconnection. This patch also enables it when any VpcPeerings exist.

Signed-off-by: Apinant U-suwantim <Hello@Apinant.dev>
(cherry picked from commit 70fe403)

Author: LoneExile

pkg/controller/vpc.go

@@ -289,7 +289,7 @@ func (c *Controller) handleAddOrUpdateVpc(key string) error {
 		return err
 	}
 
-	learnFromARPRequest := vpc.Spec.EnableExternal
+	learnFromARPRequest := vpc.Spec.EnableExternal || len(vpc.Spec.VpcPeerings) != 0
 	if !learnFromARPRequest {
 		for _, subnetName := range vpc.Status.Subnets {
 			subnet, err := c.subnetsLister.Get(subnetName)