Support type inference after using any()

[KazMiddelhoek]

This function:

def test(a: int | None, b: int | None) -> int | None:

    if any(x is None for x in [a, b]):
        return None

    return a+b

and this function:

def test_2(a: int | None, b: int | None) -> int | None:

    if a is None or b is None:
        return None

    return a+b

do the same thing. However, for the first one, mpy produces an error:

test.py:8: error: Unsupported operand types for + ("int" and "None")  [operator]
test.py:8: error: Unsupported operand types for + ("None" and "int")  [operator]
test.py:8: error: Unsupported left operand type for + ("None")  [operator]

while for the second one, the fact that a and b are not None is inferred correctly.

It would be great to improve the inference for this case!