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.Everything:

Kernel/Heap/kmalloc.cpp

@@ -242,7 +242,7 @@ void* kmalloc_impl(size_t size)
     ++g_kmalloc_call_count;
 
     if (g_dump_kmalloc_stacks && Kernel::g_kernel_symbols_available) {
-        dbg() << "kmalloc(" << size << ")";
+        dbgln("kmalloc({})", size);
         Kernel::dump_backtrace();
     }