Resolves #19246
Also related #19964

- Add KeylessAttribute in Abstractions packge
- Add convention to detect KeylessAttribute and configure the entityType to be keyless
- Scaffolding when using data annotations
  - Generate KeylessAttribute over entity class
  - Skip HasNoKey from fluent API configuration

Tests:
- Add tests for OwnedAttribute
- Add tests for KeylessAttribute
- Add test for scaffolding to verify behavior with data annotations