trace: reimplement the DTRACE function so it doesn't use a vector

At the same time, rename the trace flags to debug flags since they
have broader usage than simply tracing.  This means that
--trace-flags is now --debug-flags and --trace-help is now --debug-help

src/dev/simple_disk.cc

@@ -42,6 +42,8 @@
 
 #include "base/misc.hh"
 #include "base/trace.hh"
+#include "debug/SimpleDisk.hh"
+#include "debug/SimpleDiskData.hh"
 #include "dev/disk_image.hh"
 #include "dev/simple_disk.hh"
 #include "mem/port.hh"