WIP - support pydantic

[PythonFZ]

This PR adds support for pydantic

Old

This PR adds tests for using ZnFlow with pydantic.
The main idea would be, to use class MyCls(BaseModel, znflow.Node) like I do it with zninit.ZnInit.
Alternative approaches are also possible, e.g. providing a znflow.pydantic.Node that already provides both.

The main incompatibility seems to be:

ZnFlow/znflow/node.py

Lines 117 to 132 in 3160d0b

	def __new__(cls, *args, **kwargs):
	try:
	instance = super().__new__(cls, *args, **kwargs)
	except TypeError:
	# e.g. in dataclasses the arguments are passed to __new__
	# but even dataclasses seem to have an __init__ afterwards.
	# print("TypeError: ...")
	instance = super().__new__(cls)
	_mark_init_in_construction(cls)
	instance.uuid = uuid.uuid4()
	# Connect the Node to the Graph
	graph = get_graph()
	if graph is not empty_graph:
	graph.add_node(instance)
	return instance

But I can't tell for sure, if the __getattribute__ and __setattr__ are also affected.

One cause could be the usage of metaclass in pydantic which does not work nicely with overriding the __new__.
https://github.com/pydantic/pydantic/blob/9ab33eb82d78c55d1e66784cbd86107c1c41943d/pydantic/v1/main.py#L310