ext_authz: expose fields latency, bytesSent and bytesReceived for CEL…

… and logging (#37074)

This PR adds field access support for ext_authz filter state object
`ExtAuthzLoggingInfo`. It exposes simple fields
* latency
* bytesSent
* bytesReceived

This enables usage of ext_authz filter state in access logs, and any
filter/logger using CEL after
envoyproxy/envoy#35698.

Signed-off-by: JACQUES Francois <hypnoce@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 004e6eeaa6b4066f2ba62ca440bbcfb9fb3bc228

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

@@ -306,6 +306,9 @@ message ExtAuthz {
   //
   // If this is false the filter will not emit stats, but filter_metadata will still be respected if
   // it has a value.
+  //
+  // Field ``latency_us`` is exposed for CEL and logging when using gRPC or HTTP service.
+  // Fields ``bytesSent`` and ``bytesReceived`` are exposed for CEL and logging only when using gRPC service.
   bool emit_filter_state_stats = 29;
 }