support creation of union from generic class constructor

### Describe the Bug

```py
class A[T]:
def __init__(self, value: T):
self._value = value

def f(value: int | str):
_: A[int] | A[str] = A(value) # Argument `int | str` is not assignable to parameter `value` with type `int` in function `A.__init__`
```

here, this assignment is completey safe and valid, i would expect no error

### Sandbox Link

_No response_

### (Only applicable for extension issues) IDE Information

_No response_