Kernel: Switch singletons to use new Singleton class

Fixes #3226

Kernel/Net/UDPSocket.cpp

@@ -31,6 +31,7 @@
 #include <Kernel/Net/UDPSocket.h>
 #include <Kernel/Process.h>
 #include <Kernel/Random.h>
+#include <Kernel/Singleton.h>
 
 namespace Kernel {
 
@@ -41,11 +42,10 @@ void UDPSocket::for_each(Function<void(const UDPSocket&)> callback)
         callback(*it.value);
 }
 
+static auto s_map = make_singleton<Lockable<HashMap<u16, UDPSocket*>>>();
+
 Lockable<HashMap<u16, UDPSocket*>>& UDPSocket::sockets_by_port()
 {
-    static Lockable<HashMap<u16, UDPSocket*>>* s_map;
-    if (!s_map)
-        s_map = new Lockable<HashMap<u16, UDPSocket*>>;
     return *s_map;
 }