Remove HasNextPacket() (and fix win32)

We don't use it anymore (instead we just ReadNextPacket until it returns
an empty result).

llarp/ev/vpn.hpp

@@ -49,15 +49,10 @@ namespace llarp::vpn
     virtual std::string
     IfName() const = 0;
 
-    /// read next ip packet
-    /// blocks until ready
+    /// read next ip packet, return an empty packet if there are none ready.
     virtual net::IPPacket
     ReadNextPacket() = 0;
 
-    /// return true if we have another packet to read
-    virtual bool
-    HasNextPacket() = 0;
-
     /// write a packet to the interface
     /// returns false if we dropped it
     virtual bool

llarp/vpn/android.hpp

@@ -53,12 +53,6 @@ namespace llarp::vpn
       return sz == static_cast<ssize_t>(pkt.sz);
     }
 
-    bool
-    HasNextPacket() override
-    {
-      return false;
-    }
-
     std::string
     IfName() const override
     {

llarp/vpn/apple.hpp

@@ -122,12 +122,6 @@ namespace llarp::vpn
       return m_FD;
     }
 
-    bool
-    HasNextPacket() override
-    {
-      return false;
-    }
-
     net::IPPacket
     ReadNextPacket() override
     {

llarp/vpn/linux.hpp

@@ -108,12 +108,6 @@ namespace llarp::vpn
       return sz == static_cast<ssize_t>(pkt.sz);
     }
 
-    bool
-    HasNextPacket() override
-    {
-      return false;
-    }
-
     std::string
     IfName() const override
     {

llarp/vpn/win32.hpp

@@ -117,7 +117,7 @@ namespace llarp::vpn
     return deviceid;
   }
 
-  class Win32Interface : public NetworkInterface
+  class Win32Interface final : public NetworkInterface
   {
     std::atomic<bool> m_Run;
     HANDLE m_Device, m_IOCP;