Experiment with the Dashboard V2 schema

Can be found in grafana/grafana: https://github.com/grafana/grafana/blob/main/packages/grafana-schema/src/schema/dashboard/v2alpha0/dashboard.schema.cue

Validate that:

* [ ] cog can parse it
* [ ] cog generates valid code from it (types, builders, converters)
  * [ ] in TS
  * [ ] in Go
  * [ ] in PHP
  * [ ] in Java
* [ ]  we can use compiler passes/veneers to generate good builders from it
