[clang] [clang-tools-extra] [clangd] Support parsing comments without ASTContext (PR #78491)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > @AaronBallman @erichkeane what do you want to do here?
> 
> Because the author is no longer available for the time being, I'd recommend we close the PR. Someone can always come along to commandeer it if they have the bandwidth to work on it. WDYT?

Closing due to author nonavailability.  Commandeering encouraged!

https://github.com/llvm/llvm-project/pull/78491