tools: Fix implementation generator CLI output

Unpack the CppToC and CToCpp generator results before writing generated
content to stdout. This preserves the existing generator return contracts.

Add successful CLI regressions that verify exact output, empty stderr, and
unchanged input files.

tools/make_cpptoc_impl.py

@@ -1048,4 +1048,5 @@ if __name__ == "__main__":
     f.close()
 
   # dump the result to stdout
-  sys.stdout.write(make_cpptoc_class_impl(header, sys.argv[2], data))
+  result, _ = make_cpptoc_class_impl(header, sys.argv[2], data)
+  sys.stdout.write(result)