feat: add VM provisioning commands and compatibility checks #54

Summary #

Add the spa vm lifecycle for preparing, adopting, updating, and validating macOS bases, with compatibility enforcement before jobs run.

Changes #

• Add host and restore-image checks plus sparse base preparation, installation, boot, provisioning, adoption, and validation commands.
• Validate base ownership, manifests, product and protocol versions, and guest macOS, Swift, and Xcode capabilities.
• Update legacy guests headlessly by transferring a signed payload over the existing virtio socket protocol before atomically replacing the guest executable.
• Reject unvalidated or incompatible bases during configuration and job preparation.

Testing #

• Self-hosted macOS virtual-machine workflow

Checklist #

• Generated files are up to date.
• No credentials or unintended files are included.

Change-Id: I245147b7480fc9cd0c091e4e45a58270a6813820