WgPeerExtraData now uses OnDestroy so lifetime can be controlled

tunsafe_wg_plugin.cpp

@@ -171,6 +171,11 @@ class PluginPeer : public WgPeerExtraData {
 public:
   PluginPeer(TunsafePluginImpl *plugin, WgPeer *peer) : plugin(plugin), peer(peer), token_client_handler(this) {}
   ~PluginPeer();
+
+  virtual void OnPeerDestroy() override {
+    delete this;
+  }
+
   WgPeer *peer;
   TunsafePluginImpl *plugin;
   TokenClientHandler token_client_handler;

wireguard_proto.cpp

@@ -392,7 +392,8 @@ WgPeer::~WgPeer() {
   assert(curr_keypair_ == NULL && next_keypair_ == NULL && prev_keypair_ == NULL);
   assert(local_key_id_during_hs_ == 0);
   assert(first_queued_packet_ == NULL);
-  delete peer_extra_data_;
+  if (peer_extra_data_)
+    peer_extra_data_->OnPeerDestroy();
 }
 
 void WgPeer::DelayedDelete(void *x) {

wireguard_proto.h

@@ -468,7 +468,8 @@ private:
 // Allows associating extradata with peers that can be used by plugins etc.
 class WgPeerExtraData {
 public:
-  virtual ~WgPeerExtraData() {}
+  // This is called when the peer is destroyed.
+  virtual void OnPeerDestroy() = 0;
 };
 
 // State for peer