doesn't support async_insert

[zhenghaibing]

Setting async_insert=1, but INSERT query will be executed synchronously (reason: insert query doesn't have inlined data)

ClickHouse/ClickHouse#49308
https://clickhouse.com/docs/en/cloud/bestpractices/asynchronous-inserts

[1261385937]

@zhenghaibing https://github.com/ClickHouse/clickhouse-cpp#asynchronous-inserts
@Enmk Please close it