[MLIR] Add a foldTrait() mechanism to allow traits to define folding and test...

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

This is the same diff as https://reviews.llvm.org/D88809/ except side effect
free check is removed for involution and a FIXME is added until the dependency
is resolved for shared builds. The old diff has more details on possible fixes.

Reviewed By: rriddle, andyly

Differential Revision: https://reviews.llvm.org/D89333