bpo-40059: Add tomllib (PEP-680) (GH-31498)

This adds a new standard library module, `tomllib`, for parsing TOML.

The implementation is based on Tomli (https://github.com/hukkin/tomli).

## Steps taken (converting `tomli` to `tomllib`)

- Move everything in `tomli:src/tomli` to `Lib/tomllib`. Exclude `py.typed`.
- Remove `__version__ = ...` line from `Lib/tomllib/__init__.py`
- Move everything in `tomli:tests` to `Lib/test/test_tomllib`. Exclude the following test data dirs recursively:
  - `tomli:tests/data/invalid/_external/`
  - `tomli:tests/data/valid/_external/`
- Create `Lib/test/test_tomllib/__main__.py`:

  ```python
  import unittest

  from . import load_tests


  unittest.main()
  ```


- Add the following to `Lib/test/test_tomllib/__init__.py`:

  ```python
  import os
  from test.support import load_package_tests

  def load_tests(*args):
      return load_package_tests(os.path.dirname(__file__), *args)
  ```

  Also change `import tomli as tomllib` to `import tomllib`.

- In `cpython/Lib/tomllib/_parser.py` replace `__fp` with `fp` and `__s` with
  `s`. Add the `/` to `load` and `loads` function signatures.

- Run `make regen-stdlib-module-names`

- Create `Doc/library/tomllib.rst` and reference it in `Doc/library/fileformats.rst`

Doc/library/fileformats.rst

@@ -12,6 +12,7 @@ that aren't markup languages and are not related to e-mail.
 
    csv.rst
    configparser.rst
+   tomllib.rst
    netrc.rst
    xdrlib.rst
    plistlib.rst

Doc/library/tomllib.rst

@@ -0,0 +1,117 @@
+:mod:`tomllib` --- Parse TOML files
+===================================
+
+.. module:: tomllib
+   :synopsis: Parse TOML files.
+
+.. versionadded:: 3.11
+
+.. moduleauthor:: Taneli Hukkinen
+.. sectionauthor:: Taneli Hukkinen
+
+**Source code:** :source:`Lib/tomllib`
+
+--------------
+
+This module provides an interface for parsing TOML (Tom's Obvious Minimal
+Language, `https://toml.io <https://toml.io/en/>`_). This module does not
+support writing TOML.
+
+.. seealso::
+
+    The `Tomli-W package <https://pypi.org/project/tomli-w/>`__
+    is a TOML writer that can be used in conjunction with this module,
+    providing a write API familiar to users of the standard library
+    :mod:`marshal` and :mod:`pickle` modules.
+
+.. seealso::
+
+    The `TOML Kit package <https://pypi.org/project/tomlkit/>`__
+    is a style-preserving TOML library with both read and write capability.
+    It is a recommended replacement for this module for editing already
+    existing TOML files.
+
+
+This module defines the following functions:
+
+.. function:: load(fp, /, *, parse_float=float)
+
+   Read a TOML file. The first argument should be a readable and binary file object.
+   Return a :class:`dict`. Convert TOML types to Python using this
+   :ref:`conversion table <toml-to-py-table>`.
+
+   *parse_float* will be called with the string of every TOML
+   float to be decoded.  By default, this is equivalent to ``float(num_str)``.
+   This can be used to use another datatype or parser for TOML floats
+   (e.g. :class:`decimal.Decimal`). The callable must not return a
+   :class:`dict` or a :class:`list`, else a :exc:`ValueError` is raised.
+
+   A :exc:`TOMLDecodeError` will be raised on an invalid TOML document.
+
+
+.. function:: loads(s, /, *, parse_float=float)
+
+   Load TOML from a :class:`str` object. Return a :class:`dict`. Convert TOML
+   types to Python using this :ref:`conversion table <toml-to-py-table>`. The
+   *parse_float* argument has the same meaning as in :func:`load`.
+
+   A :exc:`TOMLDecodeError` will be raised on an invalid TOML document.
+
+
+The following exceptions are available:
+
+.. exception:: TOMLDecodeError
+
+   Subclass of :exc:`ValueError`.
+
+
+Examples
+--------
+
+Parsing a TOML file::
+
+    import tomllib
+
+    with open("pyproject.toml", "rb") as f:
+        data = tomllib.load(f)
+
+Parsing a TOML string::
+
+    import tomllib
+
+    toml_str = """
+    python-version = "3.11.0"
+    python-implementation = "CPython"
+    """
+
+    data = tomllib.loads(toml_str)
+
+
+Conversion Table
+----------------
+
+.. _toml-to-py-table:
+
++------------------+--------------------------------------------------------------------------------------+
+| TOML             | Python                                                                               |
++==================+======================================================================================+
+| table            | dict                                                                                 |
++------------------+--------------------------------------------------------------------------------------+
+| string           | str                                                                                  |
++------------------+--------------------------------------------------------------------------------------+
+| integer          | int                                                                                  |
++------------------+--------------------------------------------------------------------------------------+
+| float            | float (configurable with *parse_float*)                                              |
++------------------+--------------------------------------------------------------------------------------+
+| boolean          | bool                                                                                 |
++------------------+--------------------------------------------------------------------------------------+
+| offset date-time | datetime.datetime (``tzinfo`` attribute set to an instance of ``datetime.timezone``) |
++------------------+--------------------------------------------------------------------------------------+
+| local date-time  | datetime.datetime (``tzinfo`` attribute set to ``None``)                             |
++------------------+--------------------------------------------------------------------------------------+
+| local date       | datetime.date                                                                        |
++------------------+--------------------------------------------------------------------------------------+
+| local time       | datetime.time                                                                        |
++------------------+--------------------------------------------------------------------------------------+
+| array            | list                                                                                 |
++------------------+--------------------------------------------------------------------------------------+