Currrently the signature of `result(..)` is:
```python
result(*, infer_type: bool = False, default_factory: Callable[[], Any] | None = None, kw_only: bool = False) -> Result
```
so when users use `result(infer_type=True)`, the type checkers will
still get `kw_only=False` (from the signature), but actually the
`kw_only` should be `True` (it should follow the value of `infer_type`).
users can use `result(infer_type=True, kw_only=True)` but it's
unnecessarily verbose.
So it may introduce an incompatibility when we start to use
`dataclass_transform`. currently it's fine because we just don't use
`dataclass_transform`. But when we use, we may require a breaking
change.
This PR migrates such use to a new field specifier named
`infer_result()`.
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