Add query_kind column to system.processes table and SHOW PROCESSLIST; fix max_concurrent_select_queries bug with INTERSECT/EXCEPT

Add the query_kind column to the system.processes table and the SHOW PROCESSLIST query. Remove duplicate code. It fixes a bug: the global configuration parameter max_concurrent_select_queries was not respected to queries with INTERSECT or EXCEPT chains. #45872 (Alexey Milovidov).