Kernel: Add Socket::set_role() and use it everywhere

Instead of having Socket subclasses write their role into Socket::m_role
directly, add a setter to do this.

Kernel/Net/Socket.cpp

@@ -63,7 +63,7 @@ RefPtr<Socket> Socket::accept()
     auto& process = Process::current();
     client->set_acceptor(process);
     client->m_connected = true;
-    client->m_role = Role::Accepted;
+    client->set_role(Role::Accepted);
     if (!m_pending.is_empty())
         evaluate_block_conditions();
     return client;