Feature: `KILL` Query on request cancellation

ClickHouse Server have explicit way to cancel the long running queries via `KILL` [statement](https://clickhouse.com/docs/sql-reference/statements/kill#kill-query).

Go client should make sure to kill the query when user cancel the query request.

Begin by locating the Go client's request-cancellation handling, then review ClickHouse's KILL query documentation linked in the issue. Determine how cancellation identifies the running query and verify that cancelling a request causes the corresponding server-side query to be killed.

Written by the indexing model from the issue text.