[clang-tools-extra] [clang-doc] Add another test project to clang-doc (PR #97518)

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PeterChou1 wrote:

> I'm a bit confused by the "advanced project", as it largely seems to be minor extensions to the `basic project`. I would expect that an "advanced project" would use a complicated structure and be much larger. IMO if you're only adding some more language features, then they should be added to the existing `basic_project` already in tree.
Ok, I'll close this pr and another pr once https://github.com/llvm/llvm-project/pull/97684 is merged

https://github.com/llvm/llvm-project/pull/97518