Remove python 3.9 support from pydiverse (both transform and pipedag)

[windiana42]

We are considering to retire support for python 3.9. The main reason is that for typing unions with the pipe syntax (int | str), we need to do from __future__ import annotations, however, in case we want to analyze types in annotations, this is rather destructive because it converts the types to strings. Pydiverse transform might be first to retire 3.9. But then we might want to retire 3.9 from pydiverse pipedag on integrating the new transform version in tests.

# # try uncommenting:
# from __future__ import annotations

import inspect
import typing


def dec(fn):
    sig = inspect.signature(fn)

    def wrapper(*args, **kwargs):
        x = sig.bind(*args, **kwargs)
        print("types: " + str(typing.get_args(list(sig.parameters.values())[0].annotation)))
        return fn(*args, **kwargs)
    return wrapper

@dec
def f(a: typing.Union[int, str], **kwargs) -> int:
    return a

f(a=1)