Cue: Detect references with unifications

[spinillos]

Fixes: grafana/grafana-app-sdk#1325

Sometimes because unifications of the schema with other ones, could change the scope and Cuelang interprets it differently. It mainly happen because in App-SDK we have something like spec: _ and we unify it with the schema spec defined in Grafana apps. The result is not spec: MySpec, its spec: _ & MySpec making the spec, and depending if the fields of the schema are inside the Spec or outside, Cuelang could have different behaviour 🤷🏼‍♀️.

So instead of have:

Spec: {
  field: Disj
}

Disj: A | B

Cuelang thinks that Disj is _#def & (_#def & A | B) that its the same as (A | B) & _ (Cuelang puts the _ always at the end). So the first block is the disjunction and the second one, the value unified.

[github-actions]

Note: the diff show code changes that would be introduced by this PR to the output of the Grafana Foundation SDK codegen pipeline.

See full diff.

🔎 Changes to Grafana Foundation SDK