Added RabbitMQ storage support

Why it matters

This feature enables ClickHouse to directly consume messages from RabbitMQ, allowing seamless real-time data ingestion and integration with message queues. It solves the problem of building ETL pipelines by removing the need for intermediate tools to ingest RabbitMQ data.

How to use it

Users can create a table with the RabbitMQ engine by specifying connection parameters like host, queue name, user credentials, and format. For example:

CREATE TABLE rabbitmq_table (
  ... columns ...
) ENGINE = RabbitMQ
SETTINGS 
  rabbitmq_host = 'rabbitmq_host',
  rabbitmq_queue_name = 'queue',
  rabbitmq_user = 'user',
  rabbitmq_password = 'password',
  format = 'JSONEachRow'

This allows direct query of RabbitMQ queues as tables.