Telnetlib3

* stop using setuptools library to get current software version

* bugfix: NameError: when debug=True is used with asyncio.run, 75

* bugfix: NameError: name 'sleep' is not defined in stream_writer.py

* bugfix: "write after close" is disregarded, caused many errors logged in socket.send()
* bugfix: in accessories.repr_mapping() about using shlex.quote on non-str,
`TypeError: expected string or bytes-like object, got 'int'`
* bugfix: about fn_encoding using repr() on TelnetReaderUnicode
* bugfix: TelnetReader.is_closing() raises AttributeError
* deprecation: `TelnetReader.close` and `TelnetReader.connection_closed` emit
warning, use `at_eof()` and `feed_eof()` instead.
* deprecation: the ``loop`` argument are is no longer accepted by TelnetReader.
* enhancement: Add Generic Mud Communication Protocol support :ghissue:`63` by
gtaylor!
* change: TelnetReader and TelnetWriter no longer derive from
`asyncio.StreamReader` and `asyncio.StreamWriter`, this fixes some TypeError
in signatures and runtime

major
-----

* Support Python 3.9, 3.10, 3.11. Drop Python 3.6 and earlier, All code
and examples have been updated to the new-style PEP-492 syntax.
* the ``loop``, ``event_loop``, and ``log`` arguments are no longer accepted to
any class initializers.
* The asyncio Future, ``TelnetServer.waiter_encoding``, now receives
only a boolean, rather than an instance of TelnetServer (self).
* This release has a known memory leak when using the ``_waiter_connected`` and
``_waiter_closed`` arguments to Client or Shell class initializers, please do
not use them. A replacement "wait_for_negotiation" awaitable will be provided
in a future release.

minor
-----

- std. python telnetlib is no longer imported, its constants are
extracted directly to avoid DeprecationWarning
- some changes in CI/tox about dropping/adding python support, etc.
- skip pexpect tests with py3.10 until I can find the time to also
devote time to maintain that library to fix asyncio compatibility
issues
- small fix in repr_mapping() to use shlex to make values containing
spaces conditionally quoted
- small race condition fix for waiter_closed
- small race condition fix for repr(BaseClient) and Server,
around "peername" and in get_extra_info()

* bugfix a NoneType error on EOF/Timeout, introduced in previous
version 1.0.3, 51 by zofy.