WIP: 6458 patroni omnibus

changes in this MR:

1. remove repmgr
2. add patroni to replace repmgr. Below are 3 major issues with patroni
   1. patroni need to control postgresql service, so we need to disable postgresql runit service
   2. patroni overwrites postgresql.conf file, so chef can only updates postgresql.base.conf file which is included in postgresql.conf
   3. patroni config needs to have clear text password for a superuser and a replication user. not sure if we can allow it in gitlab.rb

documentation: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/13509/diffs

@ahmadsherif can you please review it?