Environments Cleanup
DRI: @shinya.maeda
## Problem
Stale/stopped environments build up over time. The old environments don't offer value to the user, they clutter the UI, and in the worst-case scenario, can lead to [outages](https://gitlab.com/gitlab-com/gl-infra/production/-/issues/5068).
## Proposal
Provide tools and documentation so users can manage/archive/delete environments that are no longer useful for them.
### Some specific approaches
1. Clean up stopped environments automatically with sane defaults
1. Make timing of removal configurable?
epic