general: switch to using native 3.8 versions for cached_property/Literal/Protocol instead of compat

my/core/pandas.py

@@ -5,7 +5,7 @@ Various pandas helpers and convenience functions
 # NOTE: this file is meant to be importable without Pandas installed
 from datetime import datetime
 from pprint import pformat
-from typing import Optional, TYPE_CHECKING, Any, Iterable, Type, Dict
+from typing import Optional, TYPE_CHECKING, Any, Iterable, Type, Dict, Literal
 from . import warnings, Res
 from .common import LazyLogger, Json, asdict
 
@@ -45,8 +45,6 @@ def check_dateish(s) -> Iterable[str]:
     '''.strip()
 
 
-from .compat import Literal
-
 ErrorColPolicy = Literal[
     'add_if_missing', # add error column if it's missing
     'warn'          , # warn, but do not modify