Epic: CLI for code signing

Create a CLI app that will sign code using certificates in Key Vault. The app will contain the existing functionality from the signing service; specifically, it will orchestrate unpacking container file types and support existing signing mechanisms.

The preview is scoped to existing functionality the service currently provides. Features beyond that will be prioritized for v1. The app will need to run on Windows due to Authenticode binary availability. In CI scenarios, as the recommended practice is to run signing on a separate agent than the build, this is not expected to be a significant limitation.