pam-moduler: Add test that generates a new debug module and verify it works

We mimic what pam_debug.so does by default, by implementing a similar
module fully in go, generated using pam-moduler.

This requires various utilities to generate the module and run the tests
that are in a separate internal modules so that it can be shared between
multiple implementations

.gitignore

@@ -1,3 +1,5 @@
 coverage.out
 example-module/*.so
 example-module/*.h
+cmd/pam-moduler/tests/*/*.so
+cmd/pam-moduler/tests/*/*.h