[CI] Add check-mlir-python to MLIR pre-merge checks (#72847)

PR for: https://discourse.llvm.org/t/add-check-mlir-python-to-the-mlir-pre-commit-tests/74041

It’s easy to forget about the Python bindings and not build/test them
locally. It’s also easy to change something that’ll break the python
binding tests and not find out till after you’ve committed your change.

These tests seem to run quickly and don’t require much extra setup, so
let's add them to the general MLIR pre-merge tests.