[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)

[Hsin-chieh Liu via cfe-commits]

Stehsaer wrote:

@tcottin Sorry for the late reply. I've been testing the latest commit the last 2 days.

### Feedbacks
- Bugfix: the empty detail header bug was fixed and I didn't find any other edge case yet. It's working quite well.
- H3 headers: I didn't see any problem with readability with H3 headers. They provide much better readability compared to the previous bold text.

### Additional thoughts
By reviewing the code, I found that many texts, like the texts in the header, are hard-coded. I don't know if there is any localization support (or at least a plan if localization is not yet supported) in `clangd`, but I think it is worth considering to use an approach that's easier to modify or configure (eg. access the texts from the API that `clangd` uses to read the user configuration). What do you think?

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