Webservice: re-work webserver configuration

Summary

Following #1419 (closed), re-work the configuration of Unicorn and Puma to be performed via environment variables versus separately maintained xx.rb files via ConfigMap.

Details

#1419 (closed) proposed reducing replication of unicorn.rb & puma.rb content between all sources, and having it live only within the containers.

Once the changes to the container have been merged, we can remove any further duplication of the file content from the ConfigMaps present in the gitlab/webservice chart.

We wanted to split this work off so that we don't inadvertently trip up any users who were making customizations to the contents of the ConfigMaps prior to deployment.