Queue shutdown

Add a shutdown method to queue class (threading queue, multiprocessing, asyncio) which causes all future puts to raise (a queue.QueueShutdown) and all future gets once the queue is empty to also raise, unblocking all waiters. An optional argument immediate=True will skip the requirement for the queue to be empty.

This will enable producers and consumers to use the queue to know when to stop. This is important because both producers and consumers can be blocked waiting on the queue.

Previous discussion:

• queue termination on Discourse
• #81515

Linked PRs

• gh-96474
• gh-102499
• gh-104225
• gh-104228
• gh-104230
• gh-104750
• gh-115265
• gh-115838
• gh-116699
• gh-117621
• gh-138828

开始之前，请先查看链接的 pull requests 以及之前关于 Queue 终止的讨论，因为这项工作已经在多个地方进行过探索。所请求的行为涵盖 threading queue、multiprocessing queue 和 asyncio：关闭应拒绝后续的 put、解除等待者的阻塞，并在排空后使 get 抛出异常，而 immediate=True 则跳过排空。