Add MySQL Storage Engine Settings for Connection Management

Why it matters

These settings provide better control over MySQL connections from ClickHouse by allowing automatic closing of connections, limiting the number of connection retry attempts, and configuring the size of the connection pool. This improves resource usage, reliability, and performance when integrating with MySQL.

How to use it

Users can configure the MySQL storage engine behavior by setting connection_auto_close to enable automatic closing of connections, connection_max_tries to specify the maximum number of retries for connecting, and connection_pool_size to define the number of connections maintained in the pool. These options can be set in the table engine configuration when defining or altering a MySQL table engine.