Implement automated monthly branch cleanup policy and announcement system#21299

Copilot wants to merge 2 commits intomastermicrosoft/azure-pipelines-tasks:masterfrom

copilot/fix-00bc1d7b-b157-48b2-8cae-bc4485432c2bmicrosoft/azure-pipelines-tasks:copilot/fix-00bc1d7b-b157-48b2-8cae-bc4485432c2bCopy head branch name to clipboard