Do not add kw_only dataclass fields to __match_args__ (#18892)

In runtime python does not add fields that have `kw_only` marker:
-
https://github.com/python/cpython/blob/895d983b5c9716aaaab34d14d278084b9b6730d8/Lib/dataclasses.py#L1174-L1177
-
https://github.com/python/cpython/blob/895d983b5c9716aaaab34d14d278084b9b6730d8/Lib/dataclasses.py#L411-L417

See:

```python
>>> import dataclasses
>>> @dataclasses.dataclass(kw_only=True)
... class A:
...     a: int
... 
>>> print(A.__match_args__)
()
```

Closes #18863

Author: sobolevn

mypy/plugins/dataclasses.py

@@ -381,7 +381,9 @@ def transform(self) -> bool:
         ):
             str_type = self._api.named_type("builtins.str")
             literals: list[Type] = [
-                LiteralType(attr.name, str_type) for attr in attributes if attr.is_in_init
+                LiteralType(attr.name, str_type)
+                for attr in attributes
+                if attr.is_in_init and not attr.kw_only
             ]
             match_args_type = TupleType(literals, self._api.named_type("builtins.tuple"))
             add_attribute_to_class(self._api, self._cls, "__match_args__", match_args_type)

test-data/unit/check-dataclasses.test

@@ -1847,6 +1847,22 @@ e: Empty
 reveal_type(e.__match_args__)  # N: Revealed type is "Tuple[()]"
 [builtins fixtures/dataclasses.pyi]
 
+[case testDataclassWithMatchArgsAndKwOnly]
+# flags: --python-version 3.10
+from dataclasses import dataclass, field
+@dataclass(kw_only=True)
+class One:
+    a: int
+    b: str
+reveal_type(One.__match_args__)  # N: Revealed type is "Tuple[()]"
+
+@dataclass(kw_only=True)
+class Two:
+    a: int = field(kw_only=False)
+    b: str
+reveal_type(Two.__match_args__)  # N: Revealed type is "Tuple[Literal['a']]"
+[builtins fixtures/dataclasses.pyi]
+
 [case testDataclassWithoutMatchArgs]
 # flags: --python-version 3.10
 from dataclasses import dataclass