plan replayer http dump cannot be used in a TiDB cluster with proxy

[rebelice]

Bug Report

plan replayer cannot be used in a TiDB cluster with proxy. Because it needs the address of the corresponding TiDB server.

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

It needs the address of the corresponding TiDB server.

3. What did you see instead (Required)

The address of any tidb server in the cluster is ok.

4. What is your TiDB version? (Required)

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.