Add types.ClassMethodDescriptorType for unbound class methods.

It no longer spends much time doing complex calculations and no
longer consumes much memory for creating large constants that will
be dropped later.

This fixes also bpo-21074.

This fixes also bpo-22091.

* Implement functionality
* Add documentation

* Add new fields to _PyMainInterpreterConfig:

  * executable
  * prefix
  * base_prefix
  * exec_prefix
  * base_exec_prefix

* _PySys_EndInit() now sets sys attributes from
  _PyMainInterpreterConfig

Each interpreter now has its core_config and main_config copy:

* Add _PyCoreConfig_Copy() and _PyMainInterpreterConfig_Copy()
* Move _PyCoreConfig_Read(), _PyCoreConfig_Clear() and
  _PyMainInterpreterConfig_Clear() from Python/pylifecycle.c to
  Modules/main.c
* Fix _Py_InitializeEx_Private(): call _PyCoreConfig_ReadEnv() before
  _Py_InitializeCore()

bpo-32329, bpo-32030:

* The -R option now turns on hash randomization when the
  PYTHONHASHSEED environment variable is set to 0 Previously, the
  option was ignored.
* sys.flags.hash_randomization is now properly set to 0 when hash
  randomization is turned off by PYTHONHASHSEED=0.
* _PyCoreConfig_ReadEnv() now reads the PYTHONHASHSEED environment
  variable. _Py_HashRandomization_Init() now only apply the
  configuration, it doesn't read PYTHONHASHSEED anymore.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

This part of the PEP implementation adds support for
__mro_entries__ and __class_getitem__ by updating
__build_class__ and PyObject_GetItem.

Conversions like `not a is b -> a is not b` are implemented
in AST optimizer in previous commit (7ea143ae).
So this commit removes them from peephole optimizer.

Add warnoptions and xoptions fields to _PyMainInterpreterConfig.

* Fix multiple typos in code comments

* Add spacing in comments (test_logging.py, test_math.py)

* Fix spaces at the beginning of comments in test_logging.py

Implement PEP 562: module __getattr__ and __dir__.
The implementation simply updates module_getattro and
module_dir.

CRT v142 is binary compatible with CRT v140.

_PyMainInterpreterConfig now contains Python objects, whereas
_PyCoreConfig contains wchar_t* strings.

Core config:

* Rename _PyMainInterpreterConfig_ReadEnv() to _PyCoreConfig_ReadEnv()
* Move 3 strings from _PyMainInterpreterConfig to _PyCoreConfig:
  module_search_path_env, home, program_name.
* Add _PyCoreConfig_Clear()
* _PyPathConfig_Calculate() now takes core config rather than main
  config
* _PyMainInterpreterConfig_Read() now requires also a core config

Main config:

* Add _PyMainInterpreterConfig.module_search_path: sys.path list
* Add _PyMainInterpreterConfig.argv: sys.argv list
* _PyMainInterpreterConfig_Read() now computes module_search_path

Changes:

* Split _PySys_SetArgvWithError() into subfunctions for Py_Main():

  * Create the Python list object
  * Set sys.argv to the list
  * Compute argv0
  * Prepend argv0 to sys.path

* Add _PyPathConfig_ComputeArgv0()
* Remove _PySys_SetArgvWithError()
* Py_Main() now splits the code to compute sys.argv/path0 and the
  code to update the sys module: add pymain_compute_argv()
  subfunction.

asyncio.get_event_loop(), and, subsequently asyncio._get_running_loop()
are one of the most frequently executed functions in asyncio.  They also
can't be sped up by third-party event loops like uvloop.

When implemented in C they become 4x faster.

bpo-29240, bpo-32030:

* Rename pymain_set_argv() to pymain_set_sys_argv()
* pymain_set_sys_argv() now creates of copy of argv and modify the
  copy, rather than modifying pymain->argv
* Call pymain_set_sys_argv() earlier: before pymain_run_python(), but
  after pymain_get_importer().
* Add _PySys_SetArgvWithError() to handle errors

Collect more info from builtins, resource, test.test_socket and
test.support modules.
Co-Authored-By: Christian Heimes <christian@python.org>

* Add -X utf8 command line option, PYTHONUTF8 environment variable
  and a new sys.flags.utf8_mode flag.
* If the LC_CTYPE locale is "C" at startup: enable automatically the
  UTF-8 mode.
* Add _winapi.GetACP(). encodings._alias_mbcs() now calls
  _winapi.GetACP() to get the ANSI code page
* locale.getpreferredencoding() now returns 'UTF-8' in the UTF-8
  mode. As a side effect, open() now uses the UTF-8 encoding by
  default in this mode.
* Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8 encoding
  in the UTF-8 Mode.
* Update subprocess._args_from_interpreter_flags() to handle -X utf8
* Skip some tests relying on the current locale if the UTF-8 mode is
  enabled.
* Add test_utf8mode.py.
* _Py_DecodeUTF8_surrogateescape() gets a new optional parameter to
  return also the length (number of wide characters).
* pymain_get_global_config() and pymain_set_global_config() now
  always copy flag values, rather than only copying if the new value
  is greater than the old value.

* Test atexit shutdown mechanism in a subprocess

Fix the warning:

Python/import.c: warning: comparison between signed and unsigned integer expressions
     if ((i + n + 1) <= PY_SSIZE_T_MAX / sizeof(struct _inittab)) {

test_asycio: remove also aio_path which was used when asyncio was
developed outside the stdlib.

Rather than supporting dev mode directly in the warnings module, this
instead adjusts the initialisation code to add an extra 'default'
entry to sys.warnoptions when dev mode is enabled.

This ensures that dev mode behaves *exactly* as if `-Wdefault` had
been passed on the command line, including in the way it interacts
with `sys.warnoptions`, and with other command line flags like `-bb`.

Fix also bpo-20361: have -b & -bb options take precedence over any
other warnings options.

Patch written by Nick Coghlan, with minor modifications of Victor Stinner.

It is failed with an advanced optimizer.