[mlir][python] Provide "all passes" registration module in Python

Currently, passes are registered on a per-dialect basis, which
provides the smallest footprint obviously. But for prototyping
and experimentation, a convenience "all passes" module is provided,
which registers all known MLIR passes in one run.

Usage in Python:

import mlir.all_passes_registration

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D103130