LibCore+LibIPC: Move SystemServerTakeover.{h,cpp} to LibCore

This functionality is required by Core::LocalServer and LibIPC depends
on LibCore.

take_over_accepted_socket_from_system_server has also been renamed to
take_over_socket_from_system_server as the socket need not be accepted
before taking it over. :^)

Userland/Libraries/LibCore/SystemServerTakeover.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2022, sin-ack <sin-ack@protonmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibCore/Stream.h>
+
+namespace Core {
+
+ErrorOr<NonnullOwnPtr<Core::Stream::LocalSocket>> take_over_socket_from_system_server(String const& socket_path = {});
+
+}