[clang] [clang-repl] Refactor locking of runtime PTU stack (NFC) (PR #84176)

[Stefan Gränitz via cfe-commits]

https://github.com/weliveindetail commented:

Yes sure! It requires access to the interface, but IMHO that makes a lot of sense anyway.

https://github.com/llvm/llvm-project/pull/84176