DRAFT: deprecate awaiting objects that need an async context manager

[graingert]

Closes #xxxx

• Tests added / passed
• Passes pre-commit run --all-files

very drafty experiment just to see what breaks
see also:

• async task classes are not fully implemented for Python 3.11 #6785
• [Discussion] Structured concurrency #6201

await Client() can be done by doing something like:

def create_client(*, task_status):
    async with Client(...) as client:
        task_status.started(client)
        await sleep_forever()

async with create_task_group() as tg:
    client = await tg.start(create_client)

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

       15 files  ±  0         15 suites  ±0   6h 45m 42s ⏱️ + 22m 50s
  3 007 tests +  2    2 922 ✔️ ±0    84 💤 +  2  1 ❌ ±0 
22 255 runs  +16  21 273 ✔️ +2  981 💤 +14  1 ❌ ±0 

For more details on these failures, see this check.

Results for commit 0a86d43. ± Comparison against base commit a1d2011.

♻️ This comment has been updated with latest results.