Implement transport socket match. (#8354)

Description:
Risk Level: Medium (Opt-in required)
Testing: unit test, integration tested.
Docs Changes: TODO(incfly) add an architecture docs.
Release Notes: New feature, implement `Cluster.transport_socket_matches`. Envoy can be configured to use different transport socket configuration to different endpoints based on metadata match.

Fixes #8016

Signed-off-by: Jianfei Hu <jianfeih@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ cc057ce626adb2076d3dddb8dec4628c62fc5b35

envoy/api/v2/cds.proto

@@ -161,7 +161,7 @@ message Cluster {
     // Optional endpoint metadata match criteria.
     // The connection to the endpoint with metadata matching what is set in this field
     // will use the transport socket configuration specified here.
-    // The endpoint's metadata entry in *envoy.transport_socket* is used to match
+    // The endpoint's metadata entry in *envoy.transport_socket_match* is used to match
     // against the values specified in this field.
     google.protobuf.Struct match = 2;
 
@@ -499,7 +499,6 @@ message Cluster {
   // *transport_socket_match* set, and still send plain text traffic to the same cluster.
   //
   // TODO(incfly): add a detailed architecture doc on intended usage.
-  // [#not-implemented-hide:]
   repeated TransportSocketMatch transport_socket_matches = 43;
 
   // Supplies the name of the cluster which must be unique across all clusters.

envoy/api/v3alpha/cds.proto

@@ -156,7 +156,7 @@ message Cluster {
     // Optional endpoint metadata match criteria.
     // The connection to the endpoint with metadata matching what is set in this field
     // will use the transport socket configuration specified here.
-    // The endpoint's metadata entry in *envoy.transport_socket* is used to match
+    // The endpoint's metadata entry in *envoy.transport_socket_match* is used to match
     // against the values specified in this field.
     google.protobuf.Struct match = 2;
 
@@ -495,7 +495,6 @@ message Cluster {
   // *transport_socket_match* set, and still send plain text traffic to the same cluster.
   //
   // TODO(incfly): add a detailed architecture doc on intended usage.
-  // [#not-implemented-hide:]
   repeated TransportSocketMatch transport_socket_matches = 43;
 
   // Supplies the name of the cluster which must be unique across all clusters.