Added Experimental Atomic Database Engine with Non-blocking Queries

Why it matters

The Atomic engine addresses the issue of operation blocking during table schema changes by enabling non-blocking DROP and RENAME TABLE queries. Additionally, it allows atomic swapping of tables with the EXCHANGE TABLES command. This improves concurrency, reduces downtime, and enhances table management workflows.

How to use it

To use the Atomic engine, specify it as the engine type when creating a database or table. The engine supports the non-blocking operations natively, so users can execute DROP, RENAME TABLE, and EXCHANGE TABLES t1 AND t2 commands without blocking other queries.