docs: clean up config discovery docs and make it consistent (#39918)

Mirrored from https://github.com/envoyproxy/envoy @ a1219ad35ce51f37089892cefb69c7efddd575fe

Author: update-envoy[bot]

envoy/service/extension/v3/config_discovery.proto

@@ -18,27 +18,29 @@ 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 network filters, HTTP filters, UDP session filters and Listener filters.
+// Currently, ECDS is supported for network filters, HTTP filters, UDP session 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:`Downstream Network <envoy_v3_api_field_config.listener.v3.Filter.config_discovery>`,
+// #. A filter (:ref:`Downstream Network <envoy_v3_api_field_config.listener.v3.Filter.config_discovery>`,
 //    :ref:`Upstream Network <envoy_v3_api_field_config.cluster.v3.Filter.config_discovery>`,
 //    :ref:`Listener <envoy_v3_api_field_config.listener.v3.ListenerFilter.config_discovery>`,
 //    :ref:`UDP Session <envoy_v3_api_field_extensions.filters.udp.udp_proxy.v3.UdpProxyConfig.SessionFilter.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
+//    contains a (:ref:`ExtensionConfigSource 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>`,
 //    from which the filter configuration will be fetched.
-// 2. The client then registers for a resource using the filter name as the resource_name.
-// 3. The xDS server sends back the filter's configuration.
-// 4. The client stores the configuration that will be used in the next instantiation of the filter chain,
+// #. The client then registers for a resource using the filter name as the ``resource_name``.
+// #. The xDS server sends back the filter's configuration.
+// #. The client stores the configuration that will be used in the next instantiation of the filter chain,
 //    i.e., for the next requests. Whenever an updated filter configuration arrives, it will be taken into
 //    account in the following instantiation of the filter chain.
 //
-// Note: Filters that are configured using ECDS are warmed. For more details see
-// :ref:`ExtensionConfigSource <envoy_v3_api_msg_config.core.v3.ExtensionConfigSource>`.
-
+// .. note::
+//   Filters that are configured using ECDS are warmed. For more details see
+//   :ref:`ExtensionConfigSource <envoy_v3_api_msg_config.core.v3.ExtensionConfigSource>`.
+//
 // Return extension configurations.
 service ExtensionConfigDiscoveryService {
   option (envoy.annotations.resource).type = "envoy.config.core.v3.TypedExtensionConfig";