[clang-tools-extra] [clangd] Add designator hints for parenthesis aggregate initialization (PR #170642)

[Yanzuo Liu via cfe-commits]

zwuis wrote:

I'm not sure if it is a bug. But it doesn't block this PR because no need to emit designator hints for `mem` AFAICT.

https://github.com/llvm/llvm-project/pull/170642