Function build_mysql_kv_backend 

pub async fn build_mysql_kv_backend(
    store_addrs: &[String],
    tls_config: Option<&TlsOption>,
    table_name: &str,
    max_txn_ops: usize,
) -> Result<KvBackendRef>

Builds a MySQL-backed metadata [KvBackendRef].

• store_addrs - MySQL connection URLs; only the first address is used.
• tls_config - optional TLS settings for the MySQL connection.
• table_name - metadata KV table name.
• max_txn_ops - maximum operations allowed in one metadata transaction.