ext_proc: send attributes (#30781)

Introduce the ability to send attributes in the External Processing Request

---------

Signed-off-by: Jacob Bohanon <jacob.bohanon@solo.io>

Mirrored from https://github.com/envoyproxy/envoy @ 64c6d04a5fb7b08624df6223f6ef08264b9604a5

envoy/extensions/filters/http/ext_proc/v3/ext_proc.proto

@@ -125,7 +125,6 @@ message ExternalProcessor {
   // for a reply.
   bool async_mode = 4;
 
-  // [#not-implemented-hide:]
   // Envoy provides a number of :ref:`attributes <arch_overview_attributes>`
   // for expressive policies. Each attribute name provided in this field will be
   // matched against that list and populated in the request_headers message.
@@ -133,7 +132,6 @@ message ExternalProcessor {
   // for the list of supported attributes and their types.
   repeated string request_attributes = 5;
 
-  // [#not-implemented-hide:]
   // Envoy provides a number of :ref:`attributes <arch_overview_attributes>`
   // for expressive policies. Each attribute name provided in this field will be
   // matched against that list and populated in the response_headers message.
@@ -257,12 +255,10 @@ message ExtProcOverrides {
   // Set a different asynchronous processing option than the default.
   bool async_mode = 2;
 
-  // [#not-implemented-hide:]
   // Set different optional attributes than the default setting of the
   // ``request_attributes`` field.
   repeated string request_attributes = 3;
 
-  // [#not-implemented-hide:]
   // Set different optional properties than the default setting of the
   // ``response_attributes`` field.
   repeated string response_attributes = 4;