Fix rebalance issues

[savonarola]

Fixes:

• Error formatting issues in rebalance API
  EMQX-9894
  EMQX-9895
  EMQX-9941
• wait_health_check option
  EMQX-9950

We fix error message formatting in rebalance API: previously they could be displayed as iolist dumps (internal Erlang structure).
We add wait_health_check option to node evacuation CLI and API. This is a time interval when the node reports "unhealthy status" without beginning actual evacuation. We need this to allow a Load Balancer (if any) to remove the evacuated node from balancing and not forward (re)connecting clients to the evacuated node.

emqx/emqx-docs#1925

Summary

🤖 Generated by Copilot at d32ca8b

This pull request enhances the node rebalance and evacuation features of emqx by adding a wait_health_check option to the API and CLI, improving the error message formatting, and adjusting the timeouts and options for better performance and reliability. It also updates the tests and the documentation to reflect the changes.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• Schema changes are backward compatible

[yanzhiemq]

Bug Fixes

• Fixed error message formatting in rebalance API: previously they could be displayed as unclear dumps of internal Erlang structures.

  Added wait_health_check option to node evacuation CLI and API. This is a time interval when the node reports "unhealthy status" without beginning actual evacuation. We need this to allow a Load Balancer (if any) to remove the evacuated node from balancing and not forward (re)connecting clients to the evacuated node.

[yanzhiemq]

修复

• 修复了重平衡 API 中错误消息的格式问题：之前它们可能以不清晰的 Erlang 内部结构转储的形式显示。

  在节点疏散的 CLI 和 API 中添加了 wait_health_check 选项。这是一个时间间隔，节点在此期间报告为“不健康状态”，但不会开始实际的疏散操作。我们需要这个选项来允许负载均衡器（如果有）将已疏散的节点从负载均衡中移除，并且不将（重新）连接的客户端转发到已疏散的节点。