Revert "nixos/pam: clean up generated files (no functional change) (#18580)"

This reverts commit 1010271c.
This reverts commit e85e51d4.

The first commit causes multiple regressions. The second commit tries to
fix the regressions, but does not catch all of them. There are multiple
failing tests, one of which is blocking a package update. That is not
acceptable for a cosmetic patch.