all: update to protobuf-26.0-rc2 to implement go edition features

Change-Id: I190b1550e3e2e630392fed155716af9d651c74bc
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/562615
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Stapelberg <[email protected]>
Auto-Submit: Lasse Folger <[email protected]>

integration_test.go

@@ -35,7 +35,7 @@ var (
 	regenerate   = flag.Bool("regenerate", false, "regenerate files")
 	buildRelease = flag.Bool("buildRelease", false, "build release binaries")
 
-	protobufVersion = "25.1"
+	protobufVersion = "26.0-rc2"
 
 	golangVersions = func() []string {
 		// Version policy: same version as is in the x/ repos' go.mod.

reflect/protodesc/editions_defaults.binpb

@@ -1,4 +1,4 @@
 
-
 
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reflect/protodesc/proto/go_features.proto

@@ -0,0 +1,29 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2023 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+syntax = "proto2";
+
+package google.protobuf;
+
+import "google/protobuf/descriptor.proto";
+
+extend google.protobuf.FeatureSet {
+  optional GoFeatures go = 1002;
+}
+
+message GoFeatures {
+  // Whether or not to generate the deprecated UnmarshalJSON method for enums.
+  // BEGIN GOOGLE-INTERNAL
+  // Can only be true for proto using the OPEN_V1 api.
+  // END GOOGLE-INTERNAL
+  optional bool legacy_unmarshal_json_enum = 1 [
+    retention = RETENTION_RUNTIME,
+    targets = TARGET_TYPE_ENUM,
+    edition_defaults = { edition: EDITION_PROTO2, value: "true" },
+    edition_defaults = { edition: EDITION_PROTO3, value: "false" }
+  ];
+}