[record] IHaveNew.__new__ Self return typehint (dagster-io#23213)

it appears that when installed, `@record_custom` + `IHaveNew` is
assuming `__new__` returns `None` instead of `Unknown` causing it to
believe `x` is `None` for `x = RunRecord()`

explicitly tag `__new__`'s return to `Self` to resolve

resolves dagster-io#23214

## How I Tested These Changes

manually made the change in `site-packages` of installed copy of
`1.7.13`

python_modules/dagster/dagster/_record/__init__.py

@@ -15,7 +15,7 @@
     overload,
 )
 
-from typing_extensions import dataclass_transform
+from typing_extensions import Self, dataclass_transform
 
 import dagster._check as check
 from dagster._check import EvalContext, build_check_call_str
@@ -245,7 +245,7 @@ class IHaveNew:
 
     if TYPE_CHECKING:
 
-        def __new__(cls, **kwargs): ...
+        def __new__(cls, **kwargs) -> Self: ...
 
 
 def is_record(obj) -> bool: