Product monitoring: Create concepts page

We should document that we recommend a Prometheus Servicemonitor and point to the monitoring stack.
Mention that we label all Services accordingly, so users only need to deploy a Servicemonitor and get all metrics instantly.
Provide some nice screenshots from Prometheus

This is mostly done on https://docs.stackable.tech/home/stable/operators/monitoring/
Expand it with

• some screenshots from Prometheus
• link to the monitoring stack to showcase the setup

从 docs.stackable.tech/home/stable/operators/monitoring/ 现有的 monitoring 页面开始，检查其中当前的指南。补充 Prometheus 截图、指向 monitoring stack 的链接，以及部署 Prometheus ServiceMonitor 的建议；当设置过程和 metrics 的自动收集得到清晰说明时，即视为完成。