cmd/{apidiff,gorelease}: use types.Alias when >= 1.23

This module's go.mod file specifies go1.22.
These two programs use go/types, which materializes aliases as
type.Alias when the go version is >= 1.23.
Force that materialization with toolchains >= 1.23 despite what the
go.mod says.

Fixes golang/go#70695.

Change-Id: I9401d7f80880fdf59600592baf93bb4c8b7c76ec
Reviewed-on: https://go-review.googlesource.com/c/exp/+/645015
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/apidiff/gotypesalias.go

@@ -0,0 +1,12 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.23
+
+//go:debug gotypesalias=1
+
+package main
+
+// Materialize aliases whenever the go toolchain version is after 1.23 (#69772).
+// Remove this file after go.mod >= 1.23 (which implies gotypesalias=1).

cmd/apidiff/main.go

@@ -1,3 +1,7 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 // Command apidiff determines whether two versions of a package are compatible
 package main
 

cmd/gorelease/gotypesalias.go

@@ -0,0 +1,12 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.23
+
+//go:debug gotypesalias=1
+
+package main
+
+// Materialize aliases whenever the go toolchain version is after 1.23 (#69772).
+// Remove this file after go.mod >= 1.23 (which implies gotypesalias=1).