fix(Core/Vehicles): feat vehicle seat addon, vehicle enter/exit positions (#20082)

* implement initial vehicle_seat_addon

Co-authored-by: Ovah <dreadkiller@gmx.de>

* add more vehicle_seat_addon data

* make exiting passenger visible

fixes "immediate despawn" of travelers mammoth

* style, update comments

* remove hacked pos relocate

* remove sending MSG_MOVE_ROOT/UNROOT on Ack

* set and unset UNIT_NPC_FLAG_PLAYER_VEHICLE on init/entry

* ulduar demolisher: remove flag correction and no longer needed usableseat

* fixup! implement initial vehicle_seat_addon

* fixup! fixup! implement initial vehicle_seat_addon

* re-add AddPassenger Flame Leviathan hack

was commented by mistake

* Update rev_1725993194571320983.sql

add missing ticks

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Co-authored-by: Ovah <dreadkiller@gmx.de>

src/server/game/World/World.cpp

@@ -1817,6 +1817,9 @@ void World::SetInitialWorldSettings()
     LOG_INFO("server.loading", "Loading Vehicle Accessories...");
     sObjectMgr->LoadVehicleAccessories();                       // must be after LoadCreatureTemplates() and LoadNPCSpellClickSpells()
 
+    LOG_INFO("server.loading", "Loading Vehicle Seat Addon Data...");
+    sObjectMgr->LoadVehicleSeatAddon();                         // must be after loading DBC
+
     LOG_INFO("server.loading", "Loading SpellArea Data...");                // must be after quest load
     sSpellMgr->LoadSpellAreas();