Find a trusted schema for prometheus queries

[K-Phoen]

Instead of relying on ./schemas/composable/prometheus for Grafana versions >= v11, we need to find a schema published and maintained by Grafana itself.

Schema removed by: grafana/grafana#83808

Possible replacement? https://github.com/grafana/grafana/blob/main/pkg/promlib/models/query.request.schema.json
This schema has a fair few new fields: let's check what's actually useful first.