[mlir][python][nfc] Test `-print-ir-after-all` (#75742)

The functionality to `-print-ir-after-all` was added in
https://github.com/llvm/llvm-project/commit/caa159f044a05f782701a525d8b0e8f346abbd64

.
This PR adds a test and, with that, some documentation.

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Co-authored-by: Maksim Levental <maksim.levental@gmail.com>