ecds: add dynamic config provider usage in downstream network filters (#28477)

Signed-off-by: ohadvano <ohadvano@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 1b01f90c074a410393cea6cb2fdf0ee077416957

envoy/config/listener/v3/listener_components.proto

@@ -45,7 +45,6 @@ message Filter {
     // Configuration source specifier for an extension configuration discovery
     // service. In case of a failure and without the default configuration, the
     // listener closes the connections.
-    // [#not-implemented-hide:]
     core.v3.ExtensionConfigSource config_discovery = 5;
   }
 }

envoy/service/extension/v3/config_discovery.proto

@@ -18,11 +18,12 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 // [#protodoc-title: Extension config discovery service (ECDS)]
 
 // A service that supports dynamic configuration updates for a specific filter.
-// Currently, ECDS is supported for HTTP filters and Listener filters. Please check
-// :ref:`Extension Config Discovery Service (ECDS) API <config_overview_extension_discovery>`.
+// Currently, ECDS is supported for downstream network filters, HTTP filters and Listener filters.
+// Please check :ref:`Extension Config Discovery Service (ECDS) API <config_overview_extension_discovery>`.
 // The overall extension config discovery service works as follows:
 //
-// 1. A filter (:ref:`Listener <envoy_v3_api_field_config.listener.v3.ListenerFilter.config_discovery>`
+// 1. A filter (:ref:`Network <envoy_v3_api_field_config.listener.v3.Filter.config_discovery>`,
+//    :ref:`Listener <envoy_v3_api_field_config.listener.v3.ListenerFilter.config_discovery>`
 //    or :ref:`HTTP <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpFilter.config_discovery>`)
 //    contains a :ref:`config_discovery <envoy_v3_api_msg_config.core.v3.ExtensionConfigSource>` configuration. This configuration
 //    includes a :ref:`config_source <envoy_v3_api_field_config.core.v3.ExtensionConfigSource.config_source>`,