[clang] [clang-tools-extra] [clangd] Use `SymbolName` to represent Objective-C selectors (PR #82061)

[Sam McCall via cfe-commits]

https://github.com/sam-mccall requested changes to this pull request.

As mentioned: unless there's a clear reason, I'd avoid not to add the dependency on Tooling/Refactoring as it doesn't seem to simplify the implementation much.

(My last comment should have been on the review - sorry, I'm still bad at github!)

https://github.com/llvm/llvm-project/pull/82061