[clang] [llvm] Revert "demangle function names in trace files (#87626)" (PR #102274)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> @tru @nikic @MaskRay should this be backported to 19 release branch?

Thanks for asking:) I think so. Invoked the cherry-pick command at https://github.com/llvm/llvm-project/issues/102222#issuecomment-2276883290

https://github.com/llvm/llvm-project/pull/102274