[clang-tools-extra] [clangd] Augment code completion results with documentation from the index. (PR #120099)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

Thanks. I haven't had a chance to look through the patch in detail yet, but the general shape seems reasonable.

I also wanted to check, have you resolved the issue you described in [this comment](https://github.com/clangd/clangd/issues/2252#issuecomment-2545141457)?

> now it only gives the docstring for field members and not methods

(I know the unit test covers methods, just asking in case you were seeing it not work in a real project.)

https://github.com/llvm/llvm-project/pull/120099