debug: add debug-revlog-stats command Display statistics about revlogs in the store. Useful to get an approximate size of a repository, etc. More statistics will be added in the future.

typing: attempt to remove @overloads in the platform module for stdlib methods This is mostly successful, as examining util.pyi, posix.pyi, and windows.pyi after a pytype run shows that the type overloads for `oslink`, `readlink`, `removedirs`, `rename`, `split`, and `unlink` have been removed. (Some of these still have an @overload, but the differences are the variable names, not the types.) However, @overloads remain for `abspath` and `normpath` for some reason. It's useful to redefine these methods for the type checking phase because in addition to excluding str and PathLike variants, some of these functions have optional args in stdlib that aren't implemented in the custom implementation on Windows, and we want the type checking to flag that instead of assuming it's an allowable overload everywhere. One last quirk I noticed that I can't explain- `pycompat.TYPE_CHECKING` is always False, so the conditionals need to check `typing.TYPE_CHECKING` directly. I tried dropping the custom code for assigning `pycompat.TYPE_CHECKING` and simply did `from typing import TYPE_CHECKING` directly in pycompat.py, and used `pycompat.TYPE_CHECKING` for the conditional here... and pytype complained that `pycompat` doesn't have the `TYPE_CHECKING` variable.

typing: add trivial type hints to rest of the windows platform module Skipping the file wrappers for now because there's interplay with C code, and making them subclass `typing.BinaryIO_Proxy` confuses PyCharm a bit.

typing: add type hints to the rest of the posix module These methods either don't have an analog in the windows module, or are aliased in the windows module from something else (like os.path.xxx).

typing: add type hints to the platform `cachestat` classes

util: fix the signature of observedbufferedinputpipe._fillbuffer() Flagged by PyCharm, since it didn't match the signature of the method being overridden. The default value in the superclass is also `_chunksize`, and I suspect that the amount read from `osread` should be limited to what is passed in. Only one caller (`bufferedinputpipe.unbufferedread()`) passes this argument, and it passes the max of `_chunksize` and whatever it was passed.

tests: drop some obsolete py2 handling in util.py doctest Flagged by PyCharm while inspecting imports from the platform modules.

typing: add type hints to the common posix/windows platform functions These are done in sync because some platforms have empty implementations, and it isn't obvious what the types should be without examining the other. We want the types aligned, so @overload definitions that differ aren't generated. The only differences here are the few methods that unconditionally raise an error are marked as `NoReturn`, which doesn't seem to bother pytype. A couple of the posix module functions needed to be updated with a modern ternary operator, because pytype seems to want to use the type of the second object in the old `return x and y` style.

typing: add type hints to the posix platform module matching win32.py

typing: add type hints to mercurial/win32.py These are the low level functions that are imported by the mercurial.windows module, which is in turn imported by mercurial.utils as the platform module. Pretty straightforward, but pytype inferred very little of it, likely because of the heavy ctypes usage. It also seems to trigger a pytype bug in procutil, now that it has an idea of the underlying function type, so disable that warning to maintain a working test.