PromQL coverage: validate against k8s mixin rules and awesome-prometheus-alerts

Extract all PromQL expressions from [kubernetes-mixin](https://github.com/kubernetes-monitoring/kubernetes-mixin) and [awesome-prometheus-alerts](https://github.com/samber/awesome-prometheus-alerts), classify each as fully acceleratable / partial / unsupported, and file gap issues for unsupported queries. Add the query sets as a CI regression fixture.