Delete stopped environments automatically

Description

This is continuation from #19724 (closed). Today, we have a performance issue that stopped environments still retain deployment refs. This cause performance degradation. In fact, customers also face this issue. Another example => #223155 (closed)

We should delete unnecessary environments in order to speed up git operation. This brings a lot of benefits to entire GtiLab features, especially GitLab-Runners that the total amount of refs they need to fetch will be significantly reduced.

Proposal

Delete stopped environments automatically.

Which environments will be deleted?

• The environment has already been stopped for more than a month.
• The environment is not protected.

This should also cover #225794 (closed).

Example

Given you have the following .gitlab-ci.yml:

review:
  environment:
    name: review/$CI_COMMIT_REF_NAME
    auto_stop_in: 1 week

production:
  environment: production

The outcome is:

• If the review/something environment is running for a week, it'll be stopped by environment auto-stop feature feature.
• If the review/something environment has been stopped for a month, it'll be deleted by the new feature.
• The production environment will never be stopped automatically.
• If the production environment has been stopped by manual operation, it won't be deleted because the environment was not stopped by environment auto-stop feature feature.

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