Show current deployment status of merge requests
Description including problem, use cases, benefits, and/or goals
Developers, Ops, PMs, and others should be able to quickly see if a merge request has been deployed, and if so, where it's deployed (dev, staging, prod), and quickly click through to said environment. This information should be in the activity stream (#18440 (moved)), but that isn't enough; current deployments should show up somewhere more prominently, in a fixed location.
Use the word "Released" instead of "Deployed" though.
We can split this task up into two priorities:
- Show current deploy status - Is this SHA currently deployed? - matching HEAD of branch with set of commits contained in each environment
- Show date when first deployed - bisect set of deploys or keep track of records during each deploy (see #18440 (moved))