Revert "TYP: de-duplicate some type unions (pandas-dev#341)"

This reverts commit f54d5ed.

Author: twoertwein

pandas-stubs/_typing.pyi

@@ -53,7 +53,7 @@ PandasScalar = Union[bytes, datetime.date, datetime.datetime, datetime.timedelta
 DatetimeLike = Union[datetime.date, datetime.datetime, np.datetime64, Timestamp]
 
 # dtypes
-NpDtype = Union[str, np.dtype[np.generic], type[object]]
+NpDtype = Union[str, np.dtype[np.generic], type[Union[str, complex, bool, object]]]
 Dtype = Union[ExtensionDtype, NpDtype]
 AstypeArg = Union[ExtensionDtype, npt.DTypeLike]
 # DtypeArg specifies all allowable dtypes in a functions its dtype argument
@@ -135,8 +135,12 @@ Scalar = Union[
     str,
     bytes,
     datetime.date,
+    datetime.datetime,
     datetime.timedelta,
+    bool,
     complex,
+    Timestamp,
+    Timedelta,
 ]
 ScalarT = TypeVar("ScalarT", bound=Scalar)
 # Refine the definitions below in 3.9 to use the specialized type.