[clang-tools-extra] [clang-doc] Wire Markdown parser into MDGenerator for fenced code blocks (PR #201746)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi commented:

This view is unfortunately hard to separate from the base patch, so I may have some comments that belong there.

The unfortunate part of this PR is that MDGenerator is basically deprecated and we're moving everything to the MDMustacheGenerator, similar to what happened with HTML generation.

That doesn't mean this work is useless, but I think we should focus on adding this functionality to the JSON output, and prioritize removing the legacy MD Generator. @evelez7 I think we got the Mustache version up to parity w/ the existing MD Generator, so is there any blocker to us removing it and switching everything to the Mustache version?

https://github.com/llvm/llvm-project/pull/201746