feat: configure edgecache for postgresql

- add fact to record system resolvers
- add resolvers feature in /etc/nginx/conf.d/resolvers.conf
- add rewrite rules for postgres/yum/repodata

site/profiles/manifests/edgecache/params.pp

@@ -7,6 +7,8 @@ class profiles::edgecache::params (
   Stdlib::Port $nginx_ssl_port = 443,
   Enum['http','https','both'] $nginx_listen_mode = 'http',
   Enum['puppet', 'vault']     $nginx_cert_type = 'vault',
+  Boolean $nginx_resolvers_enable = false,
+  Boolean $nginx_resolvers_ipv4only = false,
   Hash $directories = {},
   Hash $mirrors = {},
 ){