Draft: Remove hardcoded JH domain

What does this MR do and why?

Related Issue: https://jihulab.com/gitlab-cn/gitlab/-/issues/2425

支持在 gitlab.yml 配置各个环境的域名。

gitlab:
  environment_urls:
    production: "http://production.com"
    staging: "http://staging.com"
    canary: "http://canary.com"
    customer_dot_production: "http://customer.production.com"
    customer_dot_staging: "http://customer.staging.com"

How to set up and validate locally

# bin/rails console
> [Gitlab::Saas.com_url, Gitlab::Saas.staging_com_url, Gitlab::Saas.canary_toggle_com_url, Gitlab::SubscriptionPortal.default_subscriptions_url]
=> ["http://production.com", "http://staging.com", "http://canary.com", "http://customer.staging.com"]