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

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

(In the future, it would greatly help me as a reviewer if rebases are pushed separately from updates to address review comments, so that the latter get their own Compare link.)

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