net/tstun/table: add initial RoutingTable implementation

It is based on `*tempfork/device.AllowedIPs`.

Updates tailscale/corp#8020

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

tempfork/device/peer.go

@@ -7,8 +7,22 @@ package device
 
 import (
 	"container/list"
+
+	"tailscale.com/types/key"
 )
 
 type Peer struct {
 	trieEntries list.List
+
+	key key.NodePublic
+}
+
+func NewPeer(k key.NodePublic) *Peer {
+	return &Peer{
+		key: k,
+	}
+}
+
+func (p *Peer) Key() key.NodePublic {
+	return p.key
 }