mercurial/defaultrc/__init__.py

typing: make `bundlerepository` subclass `localrepository` while type checking

Currently, `mercurial/bundlerepo.py` is excluded from pytype, mostly because it
complains that various `ui` and `vfs` fields in `localrepository` are missing.
(`bundlerepository` dynamically subclasses `localrepository` when it is
instantiated, so it works at runtime.)  This makes that class hierarchy known to
pytype.

Having a protocol for `Repository` is probably the right thing to do, but that
will be a lot of work and this still reflects the class at runtime.  Subclassing
also has the benefit of making sure any method overrides have a matching
signature, so maybe this is a situation where we do both of these things.  (I'm
not sure how clear the diagnostics are if a class *almost* implements a
protocol, but is missing a method argument or similar.)  The subclassing is not
done outside of type checking runs to avoid any side effects on already complex
code.