feat: Update common protos

- List top-level request fields to be auto-populated by
  client library generators
- Explicitly mark field_behavior as non-packed

Google.Api.CommonProtos/protos/google/api/client.proto

@@ -349,6 +349,19 @@ message MethodSettings {
   //          total_poll_timeout:
   //             seconds: 54000 # 90 minutes
   LongRunning long_running = 2;
+
+  // List of top-level fields of the request message, that should be
+  // automatically populated by the client libraries based on their
+  // (google.api.field_info).format. Currently supported format: UUID4.
+  //
+  // Example of a YAML configuration:
+  //
+  //  publishing:
+  //    method_settings:
+  //      - selector: google.example.v1.ExampleService.CreateExample
+  //        auto_populated_fields:
+  //        - request_id
+  repeated string auto_populated_fields = 3;
 }
 
 // The organization for which the client libraries are being published.

Google.Api.CommonProtos/protos/google/api/field_behavior.proto

@@ -37,7 +37,7 @@ extend google.protobuf.FieldOptions {
   //   google.protobuf.Timestamp expire_time = 1
   //     [(google.api.field_behavior) = OUTPUT_ONLY,
   //      (google.api.field_behavior) = IMMUTABLE];
-  repeated google.api.FieldBehavior field_behavior = 1052;
+  repeated google.api.FieldBehavior field_behavior = 1052 [packed = false];
 }
 
 // An indicator of the behavior of a given field (for example, that a field