feat: add AutoQueue

[dxman]

AutoQueue is basically a variation on AutoChannel, which separates the acts of sending and broadcasting messages, by storing them in a BoxlessQueue. This allows users to defer processing of messages until the desired time.

Example usage:

public readonly record struct MyMessage(int Value);
// ...
var autoQueue = new AutoQueue();
var binding = autoQueue.Bind()
  .OnDequeue<MyMessage>((in msg) => GD.Print($"Value = {msg.Value}"))
// ...
autoQueue.Enqueue(new MyMessage(5));
// ...
while (autoQueue.HasValues)
{
  autoQueue.Dequeue();
}