fold ctrl layer into dbg engine - no benefit to disallowing dependence on debug engine types inside of ctrl, and it has been causing unnecessary barriers for eventual eval magic.

src/dbg_engine/dbg_engine_inc.c

@@ -2,3 +2,5 @@
 // Licensed under the MIT license (https://opensource.org/license/mit/)
 
 #include "dbg_engine_core.c"
+#include "dbg_engine_user.c"
+#include "dbg_engine_ctrl.c"