[llvm] [Lit][NFC] Refactor shell environment functionality and in-process builtins from TestRunner.py into new modules (Reopened) (PR #177358)

[Benjamin Stott via llvm-commits]

BStott6 wrote:

My bad, when incorporating 6d25af I forgot to add the future imports to the new modules. I will test with the minimum supported Python version from now on.

https://github.com/llvm/llvm-project/pull/177358