[clang-tools-extra] [clangd] Re-land "support outgoing calls in call hierarchy" (PR #117673)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> While I don't have direct experience with LLVM releases, I suppose the Outgoing Calls feature will be part of version 20?

Yep

https://github.com/llvm/llvm-project/pull/117673