[mlir] Clean up boolean flags usage in LIT tests

* Call `llvm_canonicalize_cmake_booleans` for all CMake options,
  which are propagated to `lit.local.cfg` files.
* Use Python native boolean values instead of strings for such options.

This fixes the cases, when CMake variables have values other than `ON` (like `TRUE`).
This might happen due to IDE integration or due to CMake preset usage.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D110073