[Python] support out of tree dialects and passes for python interface

[qzylalala]

Add support for out of tree dialects and passes python interface.
Note: Pybind is needed.

Please follow these commands

cmake -G Ninja .. \                                                                           
    -DMLIR_DIR=$PWD/../llvm/build/lib/cmake/mlir \
    -DLLVM_DIR=$PWD/../llvm/build/lib/cmake/llvm \
    -DLLVM_ENABLE_ASSERTIONS=ON \
    -DCMAKE_BUILD_TYPE=RELEASE \
    -DBUDDY_MLIR_ENABLE_PYTHON_PACKAGES=ON \
    -DPython3_EXECUTABLE=$(which python3)

cmake --build .

export PYTHONPATH=XXX/buddy-mlir/build/midend/python_packages/mlir_core

Then you can import our dialects and passes using python, an example is tests/Python/test_python.py

[zhanghb97]

Some quick feedback about the format.
Still reviewing the details.

[zhanghb97]

Please use Lit and FileCheck to test the code.

[qzylalala]

When I run ninja check-buddy ，I got an error like this.

check:37'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            4: ModuleNotFoundError: No module named 'buddy_mlir' 

I think this is because we don't export the right python path. The CMakeLists.txt tells us the BUDDY_MLIR_PYTHON_PACKAGES_DIR is ${BUDDY_BUILD_DIR}/python_packages

buddy-mlir/CMakeLists.txt

Line 89 in ce466ba

set(BUDDY_MLIR_PYTHON_PACKAGES_DIR ${BUDDY_BUILD_DIR}/python_packages)

And config.buddy_python_packages_dir equals to BUDDY_MLIR_PYTHON_PACKAGES_DIR.

buddy-mlir/tests/lit.site.cfg.py.in

Lines 37 to 39 in ce466ba

	config.buddy_mlir_enable_python_packages = "@BUDDY_MLIR_ENABLE_PYTHON_PACKAGES@"
	config.buddy_python_packages_dir = "@BUDDY_MLIR_PYTHON_PACKAGES_DIR@"
	config.mlir_runner_utils_dir = "@LLVM_LIBS_DIR@"

However, I set generated python packages to ${BUDDY_BUILD_DIR}/midend/python_packages/mlir_core.

And when I add this path to config.buddy_mlir_enable_python_packages, it works. So we need only one path finally.

buddy-mlir/tests/lit.cfg.py

Lines 91 to 105 in ce466ba

	if config.buddy_mlir_enable_python_packages:
	llvm_config.with_environment(
	"PYTHONPATH",
	[
	os.path.join(
	config.llvm_build_dir,
	"tools",
	"mlir",
	"python_packages",
	"mlir_core",
	),
	config.buddy_python_packages_dir,
	],
	append_path=True,
	)