Adding a No-op task executor for testing

Fixing DFS implementation of DAG validation to be much faster
Adding in additional tests to ensure the run order of expanded tasks is preserved
Adding additional compile-time checks, resolving issues that came up as a result

utils/daggyd/daggyd.cpp

@@ -95,7 +95,8 @@ void daemonize() {
 
     /* Change the working directory to the root directory */
     /* or another appropriated directory */
-    chdir("/");
+    auto rc = chdir("/");
+    (void)rc;
 
     /* Close all open file descriptors */
     for (auto x = sysconf(_SC_OPEN_MAX); x >= 0; x--) { close(x); }