bpo-47076: Make asyncio.Queue stable on slow test boxes

[asvetlov]

1. In fact, the dropped test_get_cancelled doesn't check the cancellation.
2. Reordering calls in test_blocking_get_wait makes the test more tolerant to slow execution.
3. Other await asyncio.sleep(tiny_delay) calls are removed.

https://bugs.python.org/issue47076

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @asvetlov for commit 49769ec 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.