api: use traffic_direction over operation_name if specified (#7999)

Use the listener-level field for the tracing direction over the per-filter field. Unfortunately, the per filter did not provide an "unspecified" default, so this appears to be the right approach to deprecate the per-filter field with minimal impact.

Risk Level: low (uses a newly introduce field traffic_direction)
Testing: unit test
Docs Changes: proto docs

Signed-off-by: Kuat Yessenov <kuat@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 4478c1984d17146b1ff78d0babedae2a4752b027

envoy/config/filter/network/http_connection_manager/v2/http_connection_manager.proto

@@ -79,7 +79,6 @@ message HttpConnectionManager {
   google.protobuf.BoolValue add_user_agent = 6;
 
   message Tracing {
-    // [#comment:TODO(kyessenov): Align this field with listener traffic direction field.]
     enum OperationName {
       option (gogoproto.goproto_enum_prefix) = false;
 
@@ -90,8 +89,13 @@ message HttpConnectionManager {
       EGRESS = 1;
     }
 
-    // The span name will be derived from this field.
-    OperationName operation_name = 1 [(validate.rules).enum.defined_only = true];
+    // The span name will be derived from this field. If
+    // :ref:`traffic_direction <envoy_api_field_Listener.traffic_direction>` is
+    // specified on the parent listener, then it is used instead of this field.
+    //
+    // .. attention::
+    //  This field has been deprecated in favor of `traffic_direction`.
+    OperationName operation_name = 1 [(validate.rules).enum.defined_only = true, deprecated = true];
 
     // A list of header names used to create tags for the active span. The header name is used to
     // populate the tag name, and the header value is used to populate the tag value. The tag is