Rewrite CanonicalizationConstantFoldingOpTest

The CanonicalizationConstantFoldingOpTest is currently checking if a hardcoded ir matches the system output. As the reference ir has to be updated every time the system produces an even slightly different ir, this is not maintainable.

llvm-lit provides a testing architecture to solve this. See the documentation. We also already use lit tests, see here.

The current CanonicalizationConstantFoldingOpTest should be rewritten as a lit test.