[clang-tools-extra] [clangd] Doxygen Parsing: Add proper handling of \note, \warning and \retval command + change render kind of command arguments + add preprocessing for markdown code blocks/spans (PR #156365)

[Maksim Ivanov via cfe-commits]

https://github.com/emaxx-google approved this pull request.

Looks good to me, thanks for working on this and for others to having tested it out! (The preprocessing part seems fragile though, however I don't have a better suggestion for this problem.)

https://github.com/llvm/llvm-project/pull/156365