[red-knot] Dataclasses: support `order=True` (#17406)
## Summary
Support dataclasses with `order=True`:
```py
@dataclass(order=True)
class WithOrder:
x: int
WithOrder(1) < WithOrder(2) # no error
```
Also adds some additional tests to `dataclasses.md`.
ticket: #16651
## Test Plan
New Markdown tests
