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.h

@@ -140,6 +140,8 @@ protected:
     void set_origin(Process const&);
     void set_acceptor(Process const&);
 
+    void set_role(Role role) { m_role = role; }
+
 protected:
     ucred m_origin { 0, 0, 0 };
     ucred m_acceptor { 0, 0, 0 };