LibCore: Convert CTCPSocket to ObjectPtr, add construct() helper

The C_OBJECT macro now also inserts a static construct(...) helper into
the class. Now we can make the constructor(s) private and instead call:

    auto socket = CTCPSocket::construct(arguments);

construct() returns an ObjectPtr<T>, which we'll later switch to being
a NonnullRefPtr<T>, once everything else in in place for ref-counting.

Libraries/LibCore/CTCPSocket.h

@@ -8,7 +8,9 @@ class CTCPServer;
 class CTCPSocket final : public CSocket {
     C_OBJECT(CTCPSocket)
 public:
-    explicit CTCPSocket(CObject* parent = nullptr);
-    CTCPSocket(Badge<CTCPServer>, int fd, CObject* parent = nullptr);
     virtual ~CTCPSocket() override;
+
+private:
+    CTCPSocket(int fd, CObject* parent = nullptr);
+    explicit CTCPSocket(CObject* parent = nullptr);
 };