typing: add a few type hints to `mercurial/utils/urlutil.py`

Somewhere between hg 3dbc7b1ecaba and hg 8e3f6b5bf720, `_pathsuboptions` changed
from `Dict[bytes, Tuple[bytes, Any]]` to `Dict[bytes, Tuple[str, Any]]`, and it
caught my attention from diffing the local *.pyi files.  The change is correct
based on the assertion, so let's get pytype to check for this instead of relying
on the assertion alone.

mercurial/utils/urlutil.py

@@ -9,6 +9,9 b' import re as remod'
 import socket
 
 from typing import (
+    Callable,
+    Dict,
+    Tuple,
     Union,
 )
 
@@ -29,7 +32,7 b' from ..revlogutils import ('
 )
 
 # keeps pyflakes happy
-assert [Union]
+assert [Callable, Dict, Tuple, Union]
 
 urlreq = urllibcompat.urlreq
 
@@ -652,12 +655,12 b' class paths(dict):'
             self[name] = new_paths
 
 
-_pathsuboptions = {}
+_pathsuboptions: "Dict[bytes, Tuple[str, Callable]]" = {}
 # a dictionnary of methods that can be used to format a sub-option value
 path_suboptions_display = {}
 
 
-def pathsuboption(option, attr, display=pycompat.bytestr):
+def pathsuboption(option: bytes, attr: str, display=pycompat.bytestr):
     """Decorator used to declare a path sub-option.
 
     Arguments are the sub-option name and the attribute it should set on