listener: add optional stat_prefix to use instead of listener address (#15951)

Signed-off-by: Greg Greenway <ggreenway@apple.com>

Mirrored from https://github.com/envoyproxy/envoy @ 8771f7f83cea1940a51981ac28da7b3f1b173c38

envoy/config/listener/v3/listener.proto

@@ -35,7 +35,7 @@ message ListenerCollection {
   repeated xds.core.v3.CollectionEntry entries = 1;
 }
 
-// [#next-free-field: 28]
+// [#next-free-field: 29]
 message Listener {
   option (udpa.annotations.versioning).previous_message_type = "envoy.api.v2.Listener";
 
@@ -105,6 +105,11 @@ message Listener {
   // Linux as the actual port will be allocated by the OS.
   core.v3.Address address = 2 [(validate.rules).message = {required: true}];
 
+  // Optional prefix to use on listener stats. If empty, the stats will be rooted at
+  // `listener.<address as string>.`. If non-empty, stats will be rooted at
+  // `listener.<stat_prefix>.`.
+  string stat_prefix = 28;
+
   // A list of filter chains to consider for this listener. The
   // :ref:`FilterChain <envoy_api_msg_config.listener.v3.FilterChain>` with the most specific
   // :ref:`FilterChainMatch <envoy_api_msg_config.listener.v3.FilterChainMatch>` criteria is used on a

envoy/config/listener/v4alpha/listener.proto

@@ -37,7 +37,7 @@ message ListenerCollection {
   repeated xds.core.v3.CollectionEntry entries = 1;
 }
 
-// [#next-free-field: 28]
+// [#next-free-field: 29]
 message Listener {
   option (udpa.annotations.versioning).previous_message_type = "envoy.config.listener.v3.Listener";
 
@@ -111,6 +111,11 @@ message Listener {
   // Linux as the actual port will be allocated by the OS.
   core.v4alpha.Address address = 2 [(validate.rules).message = {required: true}];
 
+  // Optional prefix to use on listener stats. If empty, the stats will be rooted at
+  // `listener.<address as string>.`. If non-empty, stats will be rooted at
+  // `listener.<stat_prefix>.`.
+  string stat_prefix = 28;
+
   // A list of filter chains to consider for this listener. The
   // :ref:`FilterChain <envoy_api_msg_config.listener.v4alpha.FilterChain>` with the most specific
   // :ref:`FilterChainMatch <envoy_api_msg_config.listener.v4alpha.FilterChainMatch>` criteria is used on a