Add support for step callback args

[goodoldneon]

Add support for step.run callback arguments.

Before this PR, step.run callbacks could only receive args via a lambda:

def do_thing(id: int) -> None:
  pass

step.run("my-step", lambda: do_thing(1))

Now you can also do this:

def do_thing(id: int) -> None:
  pass

step.run("my-step", do_thing, 1)

[masylum]

I think this broke the types for the no argument case.

[goodoldneon]

Which mypy version are you using? We're passing no arg callbacks in our tests (which we run mypy against): https://github.com/inngest/inngest-py/blob/main/tests/test_function/cases/change_step_error.py#L64