[issue46743] Enable usage of object.__orig_class__ in __init__

[Gobot1234]

Gobot1234 <gobot1234yt at gmail.com> added the comment:

```py
class DefaultBox(Generic[T]):
    def __init__(self, value: T | None = None):
        self.value = (
            value if value is not None else  # the arg
            self.__orig_class__.__args__[0]()  # or the default for the type argument 
        )

int_box = DefaultBox[int]()
print(int_box.value)  # should print 0
str_box = DefaultBox[str](value="this")
print(str_box.value)  # should print this
```
Currently this doesn't work, but I really think it should.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46743>
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