AnyStr cleanup (#5487)

* Replace all uses of StrPath, BytesPath, and AnyPath in Python 2 stubs.
* Add StrOrBytesPath as preferred alias for AnyPath.
* Replace all remaining AnyPath instances with StrOrBytesPath.
* Mark AnyPath as obsolete.

Part of #5470

stdlib/urllib/request.pyi

@@ -1,6 +1,6 @@
 import ssl
 import sys
-from _typeshed import AnyPath
+from _typeshed import StrOrBytesPath
 from email.message import Message
 from http.client import HTTPMessage, HTTPResponse, _HTTPConnectionProtocol
 from http.cookiejar import CookieJar
@@ -271,7 +271,7 @@ class HTTPErrorProcessor(BaseHandler):
 
 def urlretrieve(
     url: str,
-    filename: Optional[AnyPath] = ...,
+    filename: Optional[StrOrBytesPath] = ...,
     reporthook: Optional[Callable[[int, int, int], None]] = ...,
     data: Optional[bytes] = ...,
 ) -> Tuple[str, HTTPMessage]: ...