tempfork/device: add a temp fork of golang.zx2c4.com/wireguard/device

This will allow us to reuse the AllowedIPs for NAT decisions in a follow on commit.

The files `allowedips_*.go` are as-is, `peer.go` only keeps the `Peer` declaration with a
single element required for AllowedIPs.

Upstream commit https://git.zx2c4.com/wireguard-go/commit/?id=052af4a8072bbbd3bfe7edf46fe3c1b350f71f08

Updates tailscale/corp#8020

Signed-off-by: Maisem Ali <maisem@tailscale.com>

tempfork/device/peer.go

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+package device
+
+import (
+	"container/list"
+)
+
+type Peer struct {
+	trieEntries list.List
+}