Create the MLIR Reduce framework

Create the framework and testing environment for MLIR Reduce - a tool
with the objective to reduce large test cases into smaller ones while
preserving their interesting behavior.

Implement the functionality to parse command line arguments, parse the
MLIR test cases into modules and run the interestingness tests on
the modules.

Reviewed By: jpienaar

Differential Revision: https://reviews.llvm.org/D82803