Feature request: Support PromQL queries

[evaline-ju]

Our project using this client used to work with the legacy promlegacy Prometheus metrics, but recently, our instances were upgraded, causing all promlegacy metrics to disappear.

On the dashboard front, we can construct PromQL queries to continue viewing our metrics, but we would like to continue obtaining metrics from PromQL queries in a programmatic manner. Could support be added for PromQL queries to this client?