refactor: recreate profiles::postfix::gateway with parameterization and templates (#416)

- refactor profiles::postfix::gateway as parameterized class
- move base postfix parameters, transports, and virtuals to hiera for flexibility
- convert SMTP restrictions to arrays for better readability using join()
- add postscreen enable/disable boolean with conditional master.cf configuration
- add per-domain TLS policy maps (smtp_tls_policy_maps)
- convert alias_maps to array parameter for flexibility
- convert all postfix map files to ERB templates with parameter hashes
- add map parameters: sender_canonical_maps, sender_access_maps, relay_recipients_maps,
  relay_domains_maps, recipient_canonical_maps, recipient_access_maps, postscreen_access_maps, helo_access_maps
- move default map data to hiera while keeping parameters as empty hashes by default

This approach balances flexibility with data-driven configuration, allowing
easy customization through parameters while keeping transport/virtual maps
and default map data in hiera for role-specific overrides.

Reviewed-on: #416

hieradata/common.yaml

@@ -158,6 +158,15 @@ lookup_options:
   rke2::config_hash:
     merge:
       strategy: deep
+  postfix::configs:
+    merge:
+      strategy: deep
+  postfix::maps:
+    merge:
+      strategy: deep
+  postfix::virtuals:
+    merge:
+      strategy: deep
 
 facts_path: '/opt/puppetlabs/facter/facts.d'