Slow retrieval of configuration for Zabbix proxy due to item_rtdata

When Zabbix server is preparing configuration for Zabbix proxy it reads items by host id but later item_rtdata is retrieved by itemids, this is very slow on some installations.

Expected:
Select item_rtdata by hostid and filter out what is unneeded by using hashset search of items.
Same for item_preproc and item_parameter.