typing: add type hints to the `opener` attributes and arguments of revlog

When making revlog and filelog classes visible to pytype, it got confused quite
a bit in `mercurial/revlogutils/rewrite.py`, thinking it had a plain `Callable`,
and flagging additional methods on it like `join()` and `rename()`.  I couldn't
figure out how it reduced to that (and PyCharm flagged `opener` references as
`Any`), but this makes it happy.  So make this change before making the classes
visible.

The vfs class hierarchy is a bit wonky (e.g. `filteredvfs` is not a `vfs`), so
this may need to be revisited with a Protocol class that covers all of the `vfs`
classes.  But for now, everything works.

mercurial/revlog.py

@@ -91,6 +91,7 b' from . import ('
     revlogutils,
     templatefilters,
     util,
+    vfs as vfsmod,
 )
 from .interfaces import (
     repository,
@@ -363,9 +364,11 b' class _InnerRevlog:'
     boundaries are arbitrary and based on what we can delegate to Rust.
     """
 
+    opener: vfsmod.vfs
+
     def __init__(
         self,
-        opener,
+        opener: vfsmod.vfs,
         index,
         index_file,
         data_file,
@@ -1293,6 +1296,8 b' class revlog:'
 
     _flagserrorclass = error.RevlogError
 
+    opener: vfsmod.vfs
+
     @staticmethod
     def is_inline_index(header_bytes):
         """Determine if a revlog is inline from the initial bytes of the index"""
@@ -1311,7 +1316,7 b' class revlog:'
 
     def __init__(
         self,
-        opener,
+        opener: vfsmod.vfs,
         target,
         radix,
         postfix=None,  # only exist for `tmpcensored` now