* Update remove-stale-staging-resources workflow to completely replace undeploy workflow
* Delete the staging-undeploy-pr workflow file
* Delete all undeployment scripts and logic
* Remove all references to the automated-block-deploy label used for undeployment
* Simplify staging cross-workflow concurrency needs
* Add a script to remove stale staging deployment environments from GitHub
* Add second job to cleanup GitHub deployment environments
* Specify GITHUB_TOKEN permissions matrix
* Stop marking staging deployments as transient
* Update staging undeployment mechanism to clean-up deployment environments on PR merge
* Define a stale PR as one that was merged or has been closed for more than 2 hours
* Rename workflow file