[12501] DBScripts Engine: Support buddy search by guid

* Add new `data_flags` flag SCRIPT_FLAG_BUDDY_BY_GUID (0x10)
If this flag is set, the content of `search_distance` is interpreted as db-guid of the requested buddy

* Also switch most error log output to DB-error log output (though this will include false positives)
[12502] DBScripts Engine: Allow pets as buddy

Add new flag SCRIPT_FLAG_BUDDY_IS_PET (0x20) that will search not for a normal npc with buddy-search, but also for pets
[12503] DBScripts Engine: Change behaviour to search for a different npc when using buddy-search

With this an npc buddy will be interpreted as "another npc with entry"

Also toggle command 31 - TERMINATE_SCRIPT to also look only for other npcs of entry