This moves the puppet configuration closer to the "roles and profiles
method"[1] which is suggested for organizing puppet classes. Notably,
here it makes clear which classes are meant to be able to stand alone
as deployments.
Shims are left behind at the previous names, for compatibility with
existing `zulip.conf` files when upgrading.
[1] https://puppet.com/docs/pe/2019.8/the_roles_and_profiles_method
success-http-headers-bionic.txt and success-http-headers-focal.txt
differ only in the nginx version so this substitution will allow
us to have single file for both of them. Also this change helps
to avoid CI failure if Nginx version is updated in the OS.
Alex Vandiver
Mateusz Mandera
Anders Kaseorg
arpit551