Now that peered upstreams can generate envoy resources (#13758), we need a way to disambiguate local from peered resources in our metrics. The key difference is that datacenter and partition will be replaced with peer, since in the context of peered resources partition is ambiguous (could refer to the partition in a remote cluster or one that exists locally). The partition and datacenter of the proxy will always be that of the source service.
Regexes were updated to make emitting datacenter and partition labels mutually exclusive with peer labels.
Listener filter names were updated to better match the existing regex.
Cluster names assigned to peered upstreams were updated to be synthesized from local peer name (it previously used the externally provided primary SNI, which contained the peer name from the other side of the peering). Integration tests were updated to assert for the new peer labels.
Peered upstreams has a separate loop in xds from discovery chain upstreams. This PR adds similar but slightly modified code to add filters for peered upstream listeners, clusters, and endpoints in the case of transparent proxy.
R.B. Boyer