Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440)

Author: yusufcank34

pandas-stubs/core/indexes/base.pyi

@@ -274,6 +274,16 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
         name: Hashable = ...,
         tupleize_cols: bool = ...,
     ) -> IntervalIndex[Interval[Any]]: ...
+    @overload
+    def __new__(
+        cls,
+        data: DatetimeIndex,
+        *,
+        dtype: TimestampDtypeArg | None = ...,
+        copy: bool = ...,
+        name: Hashable = ...,
+        tupleize_cols: bool = ...,
+    ) -> DatetimeIndex: ...
     # generic overloads
     @overload
     def __new__(