New Overlapping Secrets on Azure DevOps OAuth

Introduces 'overlapping secrets' for Azure DevOps OAuth apps, allowing a new secret to be generated while the old one remains valid. This facilitates programmatic secret rotation, reduces application downtime during transitions, and enables a shortened default secret lifespan of 60 days. The feature is accessible via the ADO OAuth app pages and the Rotate Registration Secret APIs, requiring the 'vso.tokens' scope.