[runtime] Adding correct cancellation of queue tokens on queue close

[iyzhang]

This PR completes the work for cancelling pending queue tokens on close. We add a new abstraction of YielderHandles, which let other coroutines wake a yielded coroutine with an error. The woken coroutine is then expected to complete gracefully with an error. The PR is in 3 parts:

1. Add YieldHandle and other abstractions needed to support waking up yielded coroutine.
2. Add tracking to Catnap for yielded coroutines with pending operations per queue. When the operation starts, it is added to the list of pending operations and when it completes, it is removed. On close, every currently pending operation is woken with an error.
3. Add support to wait on queue tokens after close to our tests. Our testing infrastructure should wait on queue tokens after closing a socket, to ensure that they are not dangling. This finally cleans up state correctly at the end of each test.

[ppenna]

Thanks for working on this.