utest: core: move perf testcase from example to src

[unicornx]

Also:

• Add "RT_" prefix for the UTEST config options.
• Follow the naming rules to update the case name.

本 PR 仅确保 menuconfig 正常以及 test 编译正常。

[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).

---

🛠 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：dev-utest-perf
• 设置PR number为 \ Set the PR number to：10792

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 dev-utest-perf 分支，关联的 Pull Request 也会同步更新。
Once completed, commits will be pushed to the dev-utest-perf 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!

[github-actions]

📌 Code Review Assignment

🏷️ Tag: kernel

Reviewers: @GorrayLi @ReviewSun @hamburger-os @lianux-mm @wdfk-prog @xu18838022837

Changed Files (Click to expand)

• src/utest/Kconfig
• src/utest/perf/Kconfig
• src/utest/perf/README.md
• src/utest/perf/SConscript
• src/utest/perf/context_switch_tc.c
• src/utest/perf/irq_latency_tc.c
• src/utest/perf/perf_tc.c
• src/utest/perf/perf_tc.h
• src/utest/perf/thread_event_tc.c
• src/utest/perf/thread_mbox_tc.c
• src/utest/perf/thread_mq_tc.c
• src/utest/perf/thread_sem_tc.c

---

📊 Current Review Status (Last Updated: 2025-10-11 16:44 CST)

• ⌛ @GorrayLi Pending Review
• ⌛ @ReviewSun Pending Review
• ⌛ @hamburger-os Pending Review
• ⌛ @lianux-mm Pending Review
• ⌛ @wdfk-prog Pending Review
• ⌛ @xu18838022837 Pending Review

---

📝 Review Instructions

1. 维护者可以通过单击此处来刷新审查状态: 🔄 刷新状态
   Maintainers can refresh the review status by clicking here: 🔄 Refresh Status

2. 确认审核通过后评论 LGTM/lgtm
   Comment LGTM/lgtm after confirming approval

3. PR合并前需至少一位维护者确认
   PR must be confirmed by at least one maintainer before merging

ℹ️ 刷新CI状态操作需要具备仓库写入权限。
ℹ️ Refresh CI status operation requires repository Write permission.