LibCore+LibTLS: Don't keep a "ready to write" notifier on all Sockets

The "ready to write" notifier we set up in generic socket connection is
really only meant to detect a successful connection. Once we have a TCP
connection, for example, it will fire on every event loop iteration.

This was causing IRC Client to max out the CPU by getting this no-op
notifier callback over and over.

Since this was only used by TLSv12, I changed that code to create its
own notifier instead. It might be possible to improve TLS performance
by only processing writes when actually needed, but I didn't look very
closely at that for this patch. :^)

Libraries/LibTLS/Socket.cpp

@@ -142,7 +142,8 @@ bool TLSv12::common_connect(const struct sockaddr* saddr, socklen_t length)
                 if (on_tls_ready_to_read)
                     on_tls_ready_to_read(*this);
         };
-        Core::Socket::on_ready_to_write = [this] {
+        m_write_notifier = Core::Notifier::construct(fd(), Core::Notifier::Event::Write);
+        m_write_notifier->on_ready_to_write = [this] {
             if (!Core::Socket::is_open() || !Core::Socket::is_connected() || Core::Socket::eof()) {
                 // an abrupt closure (the server is a jerk)
                 dbg() << "Socket not open, assuming abrupt closure";