Adds a low-overhead mode to Channel!T that causes the buffer to be fully processed before notifying waiting peers instead of notifying immediately once data/space is available. This heavily reduces the overhead of cross-task/thread notifications at the expense of introducing processing latency and requiring a call to close() to guarantee that all data has been processed.
This change ensures that a return value of false guarantees the next call to consumeOne to succeed, meaning that the combination of empty/consumeOne is sound in a single-consumer scenario. This also updates the documentation to stress that tryConsumeOne is still the preferred API.
- allows all methods to be called on a `shared(Channel!T)` instance.
- `Channel` pre-defines the `buffer_size` argument to 100, matching `createChannel`
