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.

windows: drop some py2 registry module importing The comment was actually backwards- `winreg` is importable on py3, and is already imported by mercurial/windows.py.

typing: add type hints to the platform specific scm modules Surprisingly, pytype struggled to figure out the return types in the posix functions.

typing: add type hints to most mercurial/pycompat.py functions The `rapply` methods are left out because it's not `rapply(f, xs: _T0) -> _T0` as I first thought- it's used somewhere to walk a collection and convert between bytes and str. Also, the `open()` call is partially untyped because I'm not sure what its purpose is at this point- both the name and mode can be either bytes or str as it is currently constituted. It might make sense to assert that the file is being opened in binary mode (like `namedtempfile()`) and cast the result to `BinaryIO`, but that shouldn't be smuggled in with these other changes. The return is currently typed as `Any` because something suddenly got smarter and a few uses in util.py (like readfile()) suddenly think it returns `IO[str]` instead of `IO[bytes]` (BinaryIO), and it flags the type mismatch there.

statprof: don't pass str `sys.argv` to a function expecting bytes Found by typing the global functions in mercurial.pycompat.

typing: drop an unnecessary warning disabling comment in match.py This stopped being necessary in d2e1dcd4490d, when the exception stopped being subscripted.

scmposix: don't subscript IOError This warning disabling has been in place since late 2019 in 667f56d73ceb. We should have had some py3 support at the time, but both pytype complains and subscripting a real FileNotFoundError generated in `hg debugshell` crashed, so maybe this fixes a problem. It looks like all other instances of subscripting exceptions have been replaced (at least as far as greping for `== errno.` revealed).