[clang-tools-extra] [clangd] Allow specifying what headers are always included via "" or <> (PR #67749)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> @kleinesfilmroellchen could you rebase the patch to a recent `main` please (or merge `main` into it)?

(I just realized there is an "Update branch" button which allows me to do this from the Github UI. Apologies, one year after the project's switch away from Phabricator and I still struggle at times to get the hang of Github...)

https://github.com/llvm/llvm-project/pull/67749