Implement Durable Functions workload

Add the Durable Functions workload covering the management commands
parity with v4 (`get-history`, `get-instances`, `get-runtime-status`,
`purge-history`, `raise-event`, `rewind`, `start-new`, `terminate`,
`delete-task-hub`).

## Definition of Done

- [ ] Durable workload nupkg builds and the management commands run end
to end against a real task hub.
- [ ] All v4 `func durable` subcommands have a v5 equivalent.
- [ ] Tests cover happy path + auth failure path for each subcommand.
- [ ] Workload manifest validated by the schema in CI.

Start by locating the v4 `func durable` implementations for the nine listed management commands and the Durable workload packaging and manifest definitions. Build the workload, exercise each command against a real task hub, cover happy and authentication-failure paths, and validate the manifest with the CI schema.

Written by the indexing model from the issue text.