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.cpp

@@ -2,7 +2,7 @@
 #include <sys/socket.h>
 #include <errno.h>
 
-CTCPSocket::CTCPSocket(Badge<CTCPServer>, int fd, CObject* parent)
+CTCPSocket::CTCPSocket(int fd, CObject* parent)
     : CSocket(CSocket::Type::TCP, parent)
 {
     set_fd(fd);