this makes it easier to use `PublishWithDeferredConfirmWithContext`
without generating a custom handler that does nothing.

Add an additional example for this that also shows how to use
PublishWithDeferredConfirmWithContext.

Closes: https://github.com/wagslane/go-rabbitmq/issues/116

- 'Publish' has been deprecared by rabbitmq/ampq091-go.
 - 'PublishWithContext' has been introduced to pass context
    while publishing for cancellation.
 - Update examples to use PublishWithContext.

Signed-off-by: Aaqa Ishtyaq <aaqa@hackerrank.com>

This enables to fully utilize the given options by the amqp library.

rabbitmq/amqp091-go

It's the channel that never changes so we might
as well keep a copy of it (even to consider closing
it when the publisher is closed as well).

Also add another little buffer.

Also add a very small buffer to the NotifyReturn channel
in case no one is listening on the other side.

I event thought about actually having a timeout when sending
to that channel, but it felt it could lead to loss of
events on non problematic situations, so let's see how this
works instead.

We were probably missing those updates after a
reconnection happens, since we stayed subscribed
to the previous channel notifications instead.

- Added WithPublishOptionsExpiration which permits message expiry when the TTL has been reached
- Introduced new message var to permit the confidiontal injection of amp.Publishing options in the future.