Strengthen `Metadata` type to require version

[twschiller]

Context

• FLUP to https://github.com/pixiebrix/pixiebrix-extension/pull/9264
• Safe to do because all packages on server are required to have a version

Implementation Sketch

• Mark Metadata.version as required
• Might be able to use properties on the BrickABC/IntegrationABC/StarterBrick class to support that via computer property
  • Change BrickABC constructor to take public readonly platform: PlatformProtocol, metadata: Metadata similar to StarterBrickABC
  • Should return the PlatformProtocol.version
• Drop VersionedMetadata type