[Service Bus] Rework MessageLockCancellationToken/SessionLockCancellationToken to use events

After reviewing the proposed API with the architects, we received feedback that it would be more idiomatic to have a pattern like the following:

async Task ProcessMessage(ProcessMessageEventArgs args)
{
    using var cts = CancellationTokenSource.CreateLinkedTokenSource(args.CancellationToken);
    args.MessageLockLostAsync += cts.Cancel();

    await FooAsync(args.Message, cts.Token);
}

This means we would need to replace the MessageLockCancellationToken/SessionLockCancellationToken properties with events that can be subscribed to.

/cc @danielmarbach

[danielmarbach]

I can throw up a PR to make the API change (unless you would prefer to do this) - you already did all of the heavy lifting - I can just trigger the event when the token is signaled by using a registration.

Thanks. I’m currently on vacation and taking a bit of a break from coding. I’m back in two weeks and could pick it up if it hasn’t been done until then but I guess you want to fix this asap

[JoshLove-msft]

Another benefit of the event-based approach is that we can subclass EventArgs to allow us to flow through context data to the event. It is probably interesting to include the exception, and possibly the LockedUntilTime.