metrics: Consider secondary paths in health metrics
metrics: Consider secondary paths in health metrics

This commit changes the semantics of the `unreachable_nodes` and
`unreachable_health_endpoints` metrics to include nodes or endpoints
where the secondary path (i.e. IPv6 in dual-stack) has no connectitivty.

Signed-off-by: Sebastian Wicki <db043b2055cb3a47b2eb0b5aebf4e114a8c24a5a@isovalent.com>

cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium