Add support for per-route domains (#26847)

Signed-off-by: Jacob Neil Taylor <me@jacobtaylor.id.au>

Mirrored from https://github.com/envoyproxy/envoy @ 9acbd289ae12c0164951641931268c0824168336

envoy/extensions/filters/http/ratelimit/v3/rate_limit.proto

@@ -385,4 +385,7 @@ message RateLimitPerRoute {
   // :ref:`RouteAction.rate_limits<envoy_v3_api_field_config.route.v3.RouteAction.rate_limits>` fields instead.
   // [#not-implemented-hide:]
   repeated RateLimitConfig rate_limits = 3;
+
+  // Overrides the domain. If not set, uses the filter-level domain instead.
+  string domain = 4;
 }