Everywhere: Replace a bundle of dbg with dbgln.

These changes are arbitrarily divided into multiple commits to make it
easier to find potentially introduced bugs with git bisect.

Userland/misbehaving-application.cpp

@@ -33,7 +33,7 @@ int main(int, char**)
     Core::EventLoop event_loop;
 
     auto timer = Core::Timer::construct(10, [&] {
-        dbg() << "Now hanging!";
+        dbgln("Now hanging!");
         while (true) {
             sleep(1);
         }