Implementation of bidirection kill for kill filter. (#15240)

This allows us to more easily test response crashes.

Risk Level: low (this is a test-only filter AFAIK)
Testing: unit test, integration test
Docs Changes: Included
Release Notes: Included
Platform Specific Features: N/A
Related Issue #14249

Signed-off-by: Kevin Baichoo <kbaichoo@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 53dc7afdf139b921157155188eaf90188bf78205

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

@@ -19,10 +19,19 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 
 // Configuration for KillRequest filter.
 message KillRequest {
+  // On which direction should the filter check for the `kill_request_header`.
+  // Default to `REQUEST` if unspecified.
+  enum Direction {
+    REQUEST = 0;
+    RESPONSE = 1;
+  }
+
   // The probability that a Kill request will be triggered.
   type.v3.FractionalPercent probability = 1;
 
   // The name of the kill request header. If this field is not empty, it will override the :ref:`default header <config_http_filters_kill_request_http_header>` name. Otherwise the default header name will be used.
   string kill_request_header = 2
       [(validate.rules).string = {well_known_regex: HTTP_HEADER_VALUE strict: false}];
+
+  Direction direction = 3 [(validate.rules).enum = {defined_only: true}];
 }