Knowledge Base article about the default logging level

[rschu1ze]

A new article for the Knowledge Base, inspired by https://clickhousedb.slack.com/archives/CU478UEQZ/p1729851339838509?thread_ts=1729548744.842129&cid=CU478UEQZ

One thing that often confuses new users is that ClickHouse generates a lot of log output, even under light load. This is because the default log level is for historical reasons `trace` (instead of `warning` that would be the default in other databases). The ClickHouse developers argue that `trace` provides a lot of insight in case goes wrong. On the other hand, large volumes of logging means that system table `system.text_log` fills up quickly and needs to be merged in the background. If the database runs stable, users may re-configure the log level, see e.g. here: https://clickhouse.com/docs/en/operations/server-configuration-parameters/settings#logger