first beta!

This is the first beta (post-alpha) release of Glommio, and the first to have a Changelog.

The main change is the addition of the ScopedTask, which allows a user to create a task that is not 'static, simplifying lifetime management.

The main experimental change is the addition of the LocalExecutorPoolBuilder, which allow the user to create a group of executors all at once. This is useful in scenarios where the executors are symmetric and can all be generated from the same function.

Other notable changes:

• Using io_uring's linked SQEs, we can now timeout network requests.
• There is also a generic timeout function that can timeout any task.
• There are statistics about CPU usage coming from the LocalExecutor, so you can see which tasks are using CPU the most.
• There are statistics bout storage I/O usage coming from the Reactor, so you can see how I/O is being generated, and by each tasks.
• The mesh channel now has a send_to function, useful when you want to send one-shot messages.
• The Glommio wakers can now be used remotely from other threads. In particular, that means that Tokio channels can now be used to communicate with Glommio executors.