update benchmark data

[bengol]

What type of PR is this?

optimize

Check the PR title.

• [ Y ] This PR title match the format: \<type>(optional scope): \<description>
• [ Y ] The description of this PR title is user-oriented and clear enough for others to understand.
• [ Y ] Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

(Optional) Translate the PR title into Chinese.

更新性能压测数据

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:

1. gnet upgrade to v1.6.7
2. netpoll upgrade to v0.5.1
3. upgrade Go versiont to v1.21 when doing the benchmark
4. fix bugs to make the server & client more stable
5. update README

zh(optional):

1. gnet 更新至v1.6.7
2. netpoll 更新至v0.5.1
3. 压测时使用的 Go version更新至 1.21
4. 修复异常情况下的错误处理逻辑，使得压测程序更加健壮
5. 更新 README 文件

(Optional) Which issue(s) this PR fixes:

(optional) The PR that updates user documentation:

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