[llvm] [mlir] [MLIR] Add debug log to the pass manager (NFC) (PR #156205)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

I split the introduction of the LDBG_OS() macro in a new PR: https://github.com/llvm/llvm-project/pull/157194
This one includes the changes in LLVM from this other PR as well as the MLIR change for the pass manager (I could remove the LLVM change if needed, but since there is a single MLIR file anyway that should be fine to review).

https://github.com/llvm/llvm-project/pull/156205