Revert "[MLIR] Add a foldTrait() mechanism to allow traits to define folding...

Revert "[MLIR] Add a foldTrait() mechanism to allow traits to define folding and test it with an Involution trait"

This reverts commit 1ceaffd9.

The build is broken with  -DBUILD_SHARED_LIBS=ON ; seems like a possible
layering issue to investigate:

tools/mlir/lib/IR/CMakeFiles/obj.MLIRIR.dir/Operation.cpp.o: In function `mlir::MemoryEffectOpInterface::hasNoEffect(mlir::Operation*)':
Operation.cpp:(.text._ZN4mlir23MemoryEffectOpInterface11hasNoEffectEPNS_9OperationE[_ZN4mlir23MemoryEffectOpInterface11hasNoEffectEPNS_9OperationE]+0x9c): undefined reference to `mlir::MemoryEffectOpInterface::getEffects(llvm::SmallVectorImpl<mlir::SideEffects::EffectInstance<mlir::MemoryEffects::Effect> >&)'