switch from our custom YAML implementation to Hiera

We currently use a custom-made YAML database for assigning roles to servers and other metadata. I started using Hiera for some hosts and it seems to be working well.

Hiera is officially supported in Puppet and shipped by default in Puppet 5 and later. It's the standard way of specifying metadata and class parameters for hosts. I suspect it covers most of our needs in terms of metadata and should cover most if not all of what we're currently doing with the YAML stuff in Puppet.

We should therefore switch to using Hiera instead of our homegrown solution.

This involves converting:

• if has_role('foo') { include foo } into classes: [ 'foo' ] in hiera (DONE!)
• the $roles array into Hiera (DONE!)
• the $localinfo into Hiera (assuming all the data is there) (DONE!)
• hardcoded macros in the ferm module's me.conf.erb into exported resources (DONE, except for HOST_TPO)
• templates looping over $allnodeinfo into exported resources
• the $nodeinfo and $allnodeinfo arrays into Hiera (assuming we can switch from LDAP for host inventory)
• ./modules/torproject_org/misc/hoster.yaml
• ./modules/torproject_org/misc/local.yaml
• ./modules/ipsec/misc/config.yaml
• ./modules/roles/misc/static-components.yaml
• ./modules/roles/files/spec/spec-redirects.yaml

Ideally, all YAML data should end up in the hiera/ directory somehow. This is the first step in making our repository public (#29387) but also using Hiera as a more elaborate inventory system (#30273).

The idea of switching from LDAP to Hiera for host inventory will definitely need to be evaluated more thoroughly before going ahead with that part of the conversion, but YAML stuff in Puppet should definitely be converted.

The general goal of this is both to allow for a better inventory system but also make it easier for people to get onboarded with Puppet. By using community standards like Hiera, we make it easier for new people to get familiar with the puppet infrastructures and do things meaningfully.

Update: get_roles(), has_role(), yamlinfo() and local.yaml are all gone! The main chunks remaining are now nodeinfo(), allnodeinfo(), $nodeinfo and hoster.yaml. A plan has been laid out for that replacement below. Obviously, the ipsec, static components and redirects YAML files could use a transition into Hiera as well, but those are lower priority.