[llvm] Reland Support for mustache templating language (PR #132467)

[Paul Kirth via llvm-commits]

ilovepi wrote:

@PeterChou1 I'd like to land this soon. Can you take a look at the reland. All the ASan failures should be addressed. Also, once this lands I'd like to land the clang-doc support soon after, so I'd appreciate it if we could get those ready for a speedy review.

https://github.com/llvm/llvm-project/pull/132467