* feat(vmselect): add support for listing current running queries and canceling specific query
* fix(vmselect): change current queries' pid from int64 counter to uuid
* feat(vmselect): add auth to internal operations like `/resetRollupResultCache`, `/query/list` and `/query/kill`. add flag `internalAuthKey` for these auth
* fix(vmselect): add more info to current queries
* review: delete some unnecessary code and use function instead of init
* review: returen *queriesMap in newQueriesMap
* review: delete unused var in struct queriesMap, add comments to exported functions
* review: add return if error occurs
* feat(vmselect): truncate query string in current running query list API since the size of query string might be large;
use query string's pointer in struct `query` for the same reason;
add query info API to get full access of query's info;
