int Enum can't be used with callback factory

## Context

Non-string enums can't be used with callback data factory

For example:
```python
class MyEnum(Enum):
    foo = auto()
    bar = auto()


class MyCallback(CallbackData, prefix="my"):
    enum: MyEnum
```

## Expected Behavior

MyCallback.unpack("my:1") -> MyCallback(enum=MyEnum.foo)

## Current Behavior

Validation error