Revert "demangle function names in trace files (#87626)"
This reverts commit 0fa20c55b58deb94090985a5c5ffda4d5ceb3cd1.
Storing raw symbol names is generally preferred in profile files.
Demangling might lose information. Language frontends might use
demangling schemes not supported by LLVMDemangle
(https://github.com/llvm/llvm-project/issues/45901#issuecomment-2008686663).
In addition, calling `demangle` for each function has a significant
performance overhead (#102222).
I believe that even if we decide to provide a producer-side demangling,
it would not be on by default.
Pull Request: https://github.com/llvm/llvm-project/pull/102274
