Zero Downtime Migration with Temporal Cloud Automation

Introduces pre-release migration tooling for self-hosted Temporal to Temporal Cloud. Details the architecture involving a Migration Server and Migration Proxy for secure communication. Outlines a 5-step migration process: Preparation, Initiation, Monitoring, Validation/Handover, and Finalizing/Aborting. Highlights zero-downtime, end-to-end automation, no application code changes, minimal customer effort, and full control as key objectives. Mentions current limitations (self-hosted to Cloud only) and planned roadmap items (Cloud to self-hosted).