Anyio

- Fixed warnings caused by trio 0.15
- Worked around a compatibility issue between uvloop and Python 3.9 (missing
``shutdown_default_executor()`` method)

- Fixed compatibility with Curio 1.0
- Made it possible to assert fine grained control over which AnyIO backends and backend
options are being used with each test
- Added the ``address`` and ``peer_address`` properties to the ``SocketStream``
interface

- Repackaged release (v1.2.2 contained extra files from an experimental
branch which broke imports)

- Fixed ``CancelledError`` leaking from a cancel scope on asyncio if the task previously
received a cancellation exception
- Fixed ``AttributeError`` when cancelling a generator-based task (asyncio)
- Fixed ``wait_all_tasks_blocked()`` not working with generator-based tasks (asyncio)
- Fixed an unnecessary delay in ``connect_tcp()`` if an earlier attempt succeeds
- Fixed ``AssertionError`` in ``connect_tcp()`` if multiple connection attempts succeed
simultaneously

- Fixed cancellation errors leaking from a task group when they are contained in an
exception group
- Fixed trio v0.13 compatibility on Windows
- Fixed inconsistent queue capacity across backends when capacity was defined as 0
(trio = 0, others = infinite)
- Fixed socket creation failure crashing ``connect_tcp()``

- Added the possibility to parametrize regular pytest test functions against the
selected list of backends
- Added the ``set_total_tokens()`` method to ``CapacityLimiter``
- Added the ``anyio.current_default_thread_limiter()`` function
- Added the ``cancellable`` parameter to ``anyio.run_in_thread()``
- Implemented the Happy Eyeballs (:rfc:`6555`) algorithm for ``anyio.connect_tcp()``
- Fixed ``KeyError`` on asyncio and curio where entering and exiting a cancel scope
happens in different tasks
- Fixed deprecation warnings on Python 3.8 about the ``loop`` argument of
``asyncio.Event()``
- Forced the use ``WindowsSelectorEventLoopPolicy`` in ``asyncio.run`` when on Windows
and asyncio
to keep network functionality working
- Worker threads are now spawned with ``daemon=True`` on all backends, not just trio
- Dropped support for trio v0.11