V2 Schema Stabilization Tracking Bug

[jsuereth]

This is an issue that will track all issues / features we need to complete before declaring --v2 flags as stable.

• Support explicit exclusion for dependency resolution purposes #1455
• Ergonomic way of reusing entities #1296
• Tolerate unknown properties in resolved schema / published manifest #1365
• [wip] Forward compatibility for definition schema #1422