Add embedded Prometheus metrics endpoint support in ClickHouse Keeper.
Why it matters
The feature enables monitoring of ClickHouse Keeper by exposing internal metrics via a built-in Prometheus endpoint. This solves the problem of requiring external exporters or tools to collect Keeper metrics, allowing users to easily integrate Keeper monitoring into Prometheus-based observability setups.How to use it
Users can enable the embedded Prometheus endpoint in the ClickHouse Keeper configuration by specifying the relevant network and port settings for the metrics server. Once enabled, Prometheus can scrape metrics directly from Keeper without additional exporters.