feat(amqp): make amqp v2 compatible

[thibaudgirard]

Some methods signatures have been changed since the new version of amqp (see here: https://github.com/php-amqp/php-amqp/blob/latest/UPGRADING.md#amqpqueue-breaking-changes)

Here is the list of methods that needs to be updated:

AmqpBundle/Amqp/Consumer::class

- public function ackMessage(string $deliveryTag, int $flags = AMQP_NOPARAM): bool
+ public function ackMessage(int $deliveryTag, int $flags = AMQP_NOPARAM): void

- public function nackMessage(string $deliveryTag, int $flags = AMQP_NOPARAM): bool
+ public function nackMessage(int $deliveryTag, int $flags = AMQP_NOPARAM): void

- public function purge(): bool
+ public function purge(): void

AmqpBundle/Event/AckEvent::class & AmqpBundle/Event/NackEvent::class

- public function getDeliveryTag(): string
+ public function getDeliveryTag(): int