[Feature] Add configuration parameter to disable KILL QUERY feature

[Fiery-Fenix]

Is your feature request related to a problem? Please describe. There is an issue with KILL QUERY functionality that may unexpectedly hit ClickHouse max_concurrent_queries_for_all_users limit. Let's say in ClickHouse we have set max_concurrent_queries_for_all_users = 100. In CHProxy we have set max_concurrent_queries = 80. 20 concurrent queries is left for in some urgent/maintenance purposes. Image now situation when we have 80 heavy concurrent queries and 30 of them was discarded by end-users. CHProxy in this case will generate another 30 queries (KILL QUERY ...) that will hit ClickHouse max_concurrent_queries_for_all_users limit and we will not be able to issue any other query until enough queries will be killed. BTW ClickHouse now have dedicated settings for similar functionality - https://clickhouse.com/docs/en/operations/settings/settings/#cancel-http-readonly-queries-on-client-close

Describe the solution you'd like A new settings to disable CHProxy kill query functionality fully.