Allow non standard TLD in auto_devops_domain for testing of Auto DevOps

Description

Allow non standard TLD in auto_devops_domain for testing of Auto DevOps.

Proposal

1. Provide configuration option to disable require_valid_tld.
2. Allow users to define list of valid TLDs using valid_tlds option.

(3. Respect value set directly in the database table.)

Links / references

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/application_setting.rb#L122