Observability task: improve the health check configuration document

- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

## Describe the proposal

中文：
Dubbo目前已经实现好了健康检查，但是文档分散且不易找到。可参考[Spring Probe](https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.endpoints.kubernetes-probes)文档，对dubbo健康检查相关文档做整理。

en:
Dubbo has implemented health check, but the documents are scattered and hard to find.
you can [Spring Probe](https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.endpoints.kubernetes-probes) document, and organize relevant documents of dubbo health check.

No repository file or test is named. Start by locating the existing Dubbo health-check documentation, then compare its organization with the linked Spring Probe reference. Consolidate the relevant guidance so it is easier to find, and verify that the documentation links and documentation build remain valid.

Written by the indexing model from the issue text.