Generated hash is the same as builtin dataclass

Before:
```
class A(BaseModel):
    x: int
    y: List[int]

    class Config:
        allow_mutation = False

a = A(x=1, y=[1,2,3])
d = {a: 2}
d[a]
```
does not raise any error.

After:
It raises a Type error: "unhashable type: 'list'" because
`y` field is not hashable.

NB:
This copy the behavior of builtin dataclass where the hash
function is the hash of the *tuple* of the fields.

In the previous commit, I was using the hash of the
*dict_values* of the fields dict, which does not raise
if values are not hashable.

pydantic/main.py

@@ -313,7 +313,7 @@ def __new__(mcs, name, bases, namespace, **kwargs):  # noqa C901
             '__schema_cache__': {},
             '__json_encoder__': staticmethod(json_encoder),
             '__custom_root_type__': _custom_root_type,
-            '__hash__': (lambda self: hash(self.__dict__.values())) if not config.allow_mutation else None,
+            '__hash__': (lambda self: hash(tuple(self.__dict__.values()))) if not config.allow_mutation else None,
             **{n: v for n, v in namespace.items() if n not in fields},
         }
 

tests/test_main.py

@@ -386,7 +386,7 @@ class Config:
     assert '"TestModel" object has no field "b"' in exc_info.value.args[0]
 
 
-def test_immutable_are_hashable():
+def test_immutable_with_hashable_fields_are_hashable():
     class TestModel(BaseModel):
         a: int = 10
 
@@ -398,6 +398,20 @@ class Config:
     assert isinstance(hash(m), int)
 
 
+def test_immutable_with_unhashable_fields_are_not_hashable():
+    class TestModel(BaseModel):
+        a: int = 10
+        y: List[int] = [1, 2, 3]
+
+        class Config:
+            allow_mutation = False
+
+    m = TestModel()
+    with pytest.raises(TypeError) as exc_info:
+        hash(m)
+    assert "unhashable type: 'list'" in exc_info.value.args[0]
+
+
 def test_const_validates():
     class Model(BaseModel):
         a: int = Field(3, const=True)