Support Sphinx 7.x (#16460)

This is needed for the Debian package of mypy, as we package the docs
and we have upgraded to Sphinx 7.2.6 from 5.3.0 for the next release.
Thanks!

Bonus: Adjust many links to docs.python.org so that intersphinx can
connect them to local file for offline use.

Author: mr-c

docs/requirements-docs.txt

@@ -1,2 +1,2 @@
-sphinx>=4.2.0,<5.0.0
+sphinx>=5.1.0
 furo>=2022.3.4

docs/source/class_basics.rst

@@ -263,7 +263,7 @@ effect at runtime:
 Abstract base classes and multiple inheritance
 **********************************************
 
-Mypy supports Python :doc:`abstract base classes <library/abc>` (ABCs). Abstract classes
+Mypy supports Python :doc:`abstract base classes <python:library/abc>` (ABCs). Abstract classes
 have at least one abstract method or property that must be implemented
 by any *concrete* (non-abstract) subclass. You can define abstract base
 classes using the :py:class:`abc.ABCMeta` metaclass and the :py:func:`@abc.abstractmethod <abc.abstractmethod>`
@@ -371,8 +371,7 @@ property or an instance variable.
 Slots
 *****
 
-When a class has explicitly defined
-`__slots__ <https://docs.python.org/3/reference/datamodel.html#slots>`_,
+When a class has explicitly defined :std:term:`__slots__`,
 mypy will check that all attributes assigned to are members of ``__slots__``:
 
 .. code-block:: python

docs/source/config_file.rst

@@ -238,10 +238,8 @@ section of the command line docs.
     Crafting a single regular expression that excludes multiple files while remaining
     human-readable can be a challenge. The above example demonstrates one approach.
     ``(?x)`` enables the ``VERBOSE`` flag for the subsequent regular expression, which
-    `ignores most whitespace and supports comments`__. The above is equivalent to:
-    ``(^one\.py$|two\.pyi$|^three\.)``.
-
-    .. __: https://docs.python.org/3/library/re.html#re.X
+    :py:data:`ignores most whitespace and supports comments <re.VERBOSE>`.
+    The above is equivalent to: ``(^one\.py$|two\.pyi$|^three\.)``.
 
     For more details, see :option:`--exclude <mypy --exclude>`.
 

docs/source/error_code_list2.rst

@@ -524,8 +524,7 @@ that only existed during type-checking.
 In runtime it fails with expected ``NameError``,
 which can cause real problem in production, hidden from mypy.
 
-But, in Python3.11 ``reveal_type``
-`was added to typing.py <https://docs.python.org/3/library/typing.html#typing.reveal_type>`_.
+But, in Python3.11 :py:func:`typing.reveal_type` was added.
 ``typing_extensions`` ported this helper to all supported Python versions.
 
 Now users can actually import ``reveal_type`` to make the runtime code safe.

docs/source/getting_started.rst

@@ -256,8 +256,7 @@ Mypy can also understand how to work with types from libraries that you use.
 
 For instance, mypy comes out of the box with an intimate knowledge of the
 Python standard library. For example, here is a function which uses the
-``Path`` object from the
-`pathlib standard library module <https://docs.python.org/3/library/pathlib.html>`_:
+``Path`` object from the :doc:`pathlib standard library module <python:library/pathlib>`:
 
 .. code-block:: python
 

docs/source/html_builder.py

@@ -9,11 +9,12 @@
 from sphinx.addnodes import document
 from sphinx.application import Sphinx
 from sphinx.builders.html import StandaloneHTMLBuilder
+from sphinx.environment import BuildEnvironment
 
 
 class MypyHTMLBuilder(StandaloneHTMLBuilder):
-    def __init__(self, app: Sphinx) -> None:
-        super().__init__(app)
+    def __init__(self, app: Sphinx, env: BuildEnvironment) -> None:
+        super().__init__(app, env)
         self._ref_to_doc = {}
 
     def write_doc(self, docname: str, doctree: document) -> None:

docs/source/more_types.rst

@@ -829,7 +829,7 @@ Typing async/await
 
 Mypy lets you type coroutines that use the ``async/await`` syntax.
 For more information regarding coroutines, see :pep:`492` and the
-`asyncio documentation <https://docs.python.org/3/library/asyncio.html>`_.
+`asyncio documentation <python:library/asyncio>`_.
 
 Functions defined using ``async def`` are typed similar to normal functions.
 The return type annotation should be the same as the type of the value you