[clang-tidy][NFC] Fix list.rst and improve alias detection of `add_new_check.py` (#192228)
Follow up of https://github.com/llvm/llvm-project/pull/192224.
This commit does two things:
- Replace the original alias detection based on `:http-equiv` (we may
remove these completely in the future) with a method of directly
matching the documentation section.
- Update the list.rst
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Co-authored-by: Victor Chernyakin <chernyakin.victor.j@outlook.com>