gh-96098: Clearly link concurrent.futures from threading & multiprocessing docs (GH-96112)

Clearly link concurrent.futures from threading & multiprocessing docs

Also link directly to asyncio from the beginning of the threading docs.

Author: ncoghlan

Doc/library/multiprocessing.rst

@@ -45,6 +45,16 @@ will print to standard output ::
    [1, 4, 9]
 
 
+.. seealso::
+
+   :class:`concurrent.futures.ProcessPoolExecutor` offers a higher level interface
+   to push tasks to a background process without blocking execution of the
+   calling process. Compared to using the :class:`~multiprocessing.pool.Pool`
+   interface directly, the :mod:`concurrent.futures` API more readily allows
+   the submission of work to the underlying process pool to be separated from
+   waiting for the results.
+
+
 The :class:`Process` class
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 

Doc/library/threading.rst

@@ -9,11 +9,23 @@
 --------------
 
 This module constructs higher-level threading interfaces on top of the lower
-level :mod:`_thread` module.  See also the :mod:`queue` module.
+level :mod:`_thread` module.
 
 .. versionchanged:: 3.7
    This module used to be optional, it is now always available.
 
+.. seealso::
+
+   :class:`concurrent.futures.ThreadPoolExecutor` offers a higher level interface
+   to push tasks to a background thread without blocking execution of the
+   calling thread, while still being able to retrieve their results when needed.
+
+   :mod:`queue` provides a thread-safe interface for exchanging data between
+   running threads.
+
+   :mod:`asyncio` offers an alternative approach to achieving task level
+   concurrency without requiring the use of multiple operating system threads.
+
 .. note::
 
    In the Python 2.x series, this module contained ``camelCase`` names

Misc/NEWS.d/next/Documentation/2022-08-19-17-07-45.gh-issue-96098.nDp43u.rst

@@ -0,0 +1,3 @@
+Improve discoverability of the higher level concurrent.futures module by
+providing clearer links from the lower level threading and multiprocessing
+modules.