Kernel: Add a NetworkTask and a received network packet queue.

It will be easier to deal with incoming packets in a separate task.

Kernel/MACAddress.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <AK/Assertions.h>
+#include <AK/AKString.h>
 #include <AK/Types.h>
 #include <Kernel/StdLib.h>
 
@@ -19,6 +20,11 @@ public:
         return m_data[i];
     }
 
+    String to_string() const
+    {
+        return String::format("%b:%b:%b:%b:%b:%b", m_data[0], m_data[1], m_data[2], m_data[3], m_data[4], m_data[5]);
+    }
+
 private:
     byte m_data[6];
 };