[utest]Remove all posix test cases from utest.

[Rbb666]

移除所有关于 posix 相关的测试用例文件，避免GPL污染。

后续考虑制作成软件包形式存在。

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

为确保代码符合 RT-Thread 的编码规范，请在你的仓库中执行以下步骤运行代码格式化工作流（如果格式化CI运行失败）。
To ensure your code complies with RT-Thread's coding style, please run the code formatting workflow by following the steps below (If the formatting of CI fails to run).

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🛠 操作步骤 | Steps

1. 前往 Actions 页面 | Go to the Actions page
   点击进入工作流 → | Click to open workflow →

2. 点击 Run workflow | Click Run workflow

• 设置需排除的文件/目录（目录请以"/"结尾）
  Set files/directories to exclude (directories should end with "/")
• 将目标分支设置为 \ Set the target branch to：posix
• 设置PR number为 \ Set the PR number to：10804

3. 等待工作流完成 | Wait for the workflow to complete
   格式化后的代码将自动推送至你的分支。
   The formatted code will be automatically pushed to your branch.

完成后，提交将自动更新至 posix 分支，关联的 Pull Request 也会同步更新。
Once completed, commits will be pushed to the posix branch automatically, and the related Pull Request will be updated.

如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[unicornx]

该 pr merge 后将解决

• [Bug] examples/utest/testcases/posix 下部分代码是 GPL 的，和 RT-Thread 的 Apache 授权冲突 #9796