[llvm] [Lit][NFC] Refactor shell environment functionality and in-process builtins from TestRunner.py into new modules (PR #176761)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

This looks like a pretty straight forward improvement.

But I'm not sure I understand the overall design. It looks like the plan is to make it so that builtins can be defined in a local lit config. How exactly does that enable daemonization? You need to have a persistent process pool. Do you just maintain that within the lit config as well (maybe with some helper functions)?

https://github.com/llvm/llvm-project/pull/176761